Method for electrochemically depositing metal on a semiconductor workpiece

ABSTRACT

A process for metallization of a workpiece, such as a semiconductor workpiece. In an embodiment, an alkaline electrolytic copper bath is used to electroplate copper onto a seed layer, electroplate copper directly onto a barrier layer material, or enhance an ultra-thin copper seed layer which has been deposited on the barrier layer using a deposition process such as PVD. The resulting copper layer provides an excellent conformal copper coating that fills trenches, vias, and other microstructures in the workpiece. When used for seed layer enhancement, the resulting copper seed layer provide an excellent conformal copper coating that allows the microstructures to be filled with a copper layer having good uniformity using electrochemical deposition techniques. Further, copper layers that are electroplated in the disclosed manner exhibit low sheet resistance and are readily annealed at low temperatures.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 09/387,099, filed Aug. 31, 1999, now U.S. Pat. No. 6,277,263,which is a continuation of International Patent Application No.PCT/US99/06306, filed Mar. 22, 1999, designating the United States,which is a continuation-in-part of U.S. patent application Ser. No.09/045,245, filed Mar. 20, 1998, and now U.S. Pat. No. 6,197,181, andclaiming the benefit of U.S. Provisional Patent Application No.60/085,675, filed May 15, 1998; and is a continuation of InternationalPatent Application No. PCT/US00/10120, filed Apr. 13, 2000, designatingthe United States and claiming the benefit of U.S. Provisional PatentApplication Nos. 60/182,160, filed Feb. 14, 2000; No. 60/143,769, filedJul. 12, 1999, and No. 60/129,055, filed Apr. 13, 1999; and claims thebenefit of U.S. Provisional Patent Application No. 60/206,663, filed May24, 2000, the disclosures of each of which are hereby expresslyincorporated by reference.

FIELD OF THE INVENTION

The present invention relates to electrochemical processing ofworkpieces, and particularly for processes, apparatus and chemicalsolutions for depositing metals on microelectronic and micromechanicalworkpieces.

BACKGROUND OF THE INVENTION

In the fabrication of microelectronic devices, application of one ormore metallization layers is often an important step in the overallfabrication process. The metallization may be used in the formation ofdiscrete microelectronic components, such as read/write heads, but it ismore often used to interconnect components formed on a workpiece, suchas a semiconductor workpiece. For example, such structures are used tointerconnect the devices of an integrated circuit.

A basic understanding of certain terms used herein will assist thereader in understanding the disclosed subject matter. To this end, basicdefinitions of certain terms, as used in the present disclosure, are setforth below.

Single Metallization Level is defined as a composite level of aworkpiece that is exterior to the substrate. The composite levelcomprises one or more metal structures.

Substrate is defined as a base layer of material over which one or moremetallization levels are disposed. The substrate may be, for example, asemiconductor, a ceramic, etc.

Workpiece is defined as an object that at least comprises a substrate,and may include further layers of material or manufactured components,such as one or more metallization levels, disposed on the substrate. Theworkpiece may be, for example, a semiconductor wafer, a micromechanicaldevice, or other device.

An integrated circuit is an interconnected ensemble of devices formedwithin a semiconductor material and within a dielectric material thatoverlies a surface of the semiconductor. Devices which may be formedwithin the semiconductor include MOS transistors, bipolar transistors,diodes and diffused resistors. Devices which may be formed within thedielectric include thin-film resistors and capacitors. Typically, morethan 100 integrated circuit die (IC chips) are constructed on a single 8inch diameter silicon wafer. The devices utilized in each dice areinterconnected by conductor paths formed within the dielectric.Typically, two or more levels of conductor paths, with successive levelsseparated by a dielectric layer, are employed as interconnections. Incurrent practice, an aluminum alloy and silicon oxide are typically usedfor, respectively, the conductor and dielectric.

Delays in propagation of electrical signals between devices on a singledie limit the performance of integrated circuits. More particularly,these delays limit the speed at which an integrated circuit may processthese electrical signals. Larger propagation delays reduce the speed atwhich the integrated circuit may process the electrical signals, whilesmaller propagation delays increase this speed. Accordingly, integratedcircuit manufacturers seek ways in which to reduce the propagationdelays.

For each interconnect path, signal propagation delay may becharacterized by a time delay τ. See E. H. Stevens, InterconnectTechnology, QMC, Inc., Jul. 1993. An approximate expression for the timedelay, τ, as it relates to the transmission of a signal betweentransistors on an integrated circuit is given below.

τ=RC[1+(V _(SAT/) /RI _(SAT))]

In this equation, R and C are, respectively, an equivalent resistanceand capacitance for the interconnect path and I_(SAT) and V_(SAT) are,respectively, the saturation (maximum) current and the drain-to-sourcepotential at the onset of current saturation for the transistor thatapplies a signal to the interconnect path. The path resistance isproportional to the resistivity, ρ, of the conductor material. The pathcapacitance is proportional to the relative dielectric permittivity,K_(e), of the dielectric material. A small value of τ requires that theinterconnect line carry a current density sufficiently large to make theratio V_(SAT/)/RI_(SAT) small. It follows therefore, that a low-ρconductor which can carry a high current density and a low-K_(e)dielectric must be utilized in the manufacture of high-performanceintegrated circuits.

To meet the foregoing criterion, copper interconnect lines within alow-K_(e) dielectric will likely replace aluminum-alloy lines within asilicon oxide dielectric as the most suitable interconnect structure.See “Copper Goes Mainstream: Low-k to Follow”, SemiconductorInternational, November 1997, pp. 67-70. Resistivities of copper filmsare in the range of 1.7 to 2.0 μΩcm.; resistivities of aluminum-alloyfilms are in the range of 3.0 to 3.5 μΩcm.

Despite the advantageous properties of copper, it has not been as widelyused as an interconnect material as one would expect. This is due, atleast in part, to the difficulty of depositing copper metallization and,further, due to the need for the presence of barrier layer materials.The need for a barrier layer arises from the tendency of copper todiffuse into silicon junctions and alter the electrical characteristicsof the semiconductor devices formed in the substrate. Barrier layersmade of, for example, titanium nitride, tantalum nitride, etc., must belaid over the silicon junctions and any intervening layers prior todepositing a layer of copper to prevent such diffusion.

A number of processes for applying copper metallization to semiconductorworkpieces have been developed in recent years. One such process ischemical vapor deposition (CVD), in which a thin copper film is formedon the surface of the barrier layer by thermal decomposition and/orreaction of gas phase copper compositions. A CVD process can result inconformal copper coverage over a variety of topological profiles, butsuch processes are expensive when used to implement an entiremetallization layer.

Another known technique, physical vapor deposition (PVD), can readilydeposit copper on the barrier layer with relatively good adhesion whencompared to CVD processes. One disadvantage of PVD processes, however,is that they result in poor (non-conformal) step coverage when used tofill microstructures, such as vias and trenches, disposed in the surfaceof the semiconductor workpiece. For example, such non-conformal coverageresults in less copper deposition at the bottom and especially on thesidewalls of trenches in the semiconductor devices.

Inadequate deposition of a PVD copper layer into a trench to form aninterconnect line in the plane of a metallization layer is illustratedin FIG. 1. As illustrated, the upper portion of the trench iseffectively “pinched off” before an adequate amount of copper has beendeposited within the lower portions of the trench. This result in anopen void region that seriously impacts the ability of the metallizationline to carry the electrical signals for which it was designed.

Electrochemical deposition of copper has been found to provide the mostcost-effective manner in which to deposit a copper metallization layer.In addition to being economically viable, such deposition techniquesprovide substantially conformal copper films that are mechanically andelectrically suitable for interconnect structures. These techniques,however, are generally only suitable for applying copper to anelectrically conductive layer. As such, an underlying conductive seedlayer is generally applied to the workpiece before it is subject to anelectrochemical deposition process. Techniques for electrodeposition ofcopper on a barrier layer material have not heretofore been commerciallyviable.

The present inventors have recognized that there exists a need toprovide copper metallization processing techniques that 1) provideconformal copper coverage with adequate adhesion to the barrier layer,2) provide adequate deposition speeds, and 3) are commercially viable.These needs are met by the apparatus and processes of the presentinvention as described below.

BRIEF SUMMARY OF THE INVENTION

The present invention provides processes and apparatus for enhancing orrepairing ultra-thin or incomplete metal seed layers that have beendeposited on a workpiece, using electrolytic or electroless platingbaths, in an electrodeposition reactor that is designed and adaptablefor substrates having differing electrical properties.

One embodiment of the invention provides a process for applying ametallization interconnect structure to a workpiece on which anultra-thin metal seed layer has been formed using a first depositionprocess. The first deposition process anchors the ultra-thin metal seedlayer to an underlying layer, the ultra-thin metal seed layer havingphysical characteristics that render it generally unsuitable for bulkelectrolytic deposition of a metal onto the metal seed layer. Theprocess entails repairing the ultra-thin metal seed layer byelectrochemically depositing additional metal on the ultra-thin metalseed layer within a principal fluid chamber of a reactor to provide anenhanced seed layer using a second deposition process. The seconddeposition process, which is different from the first depositionprocess, entails supplying electroplating power to a plurality ofconcentric anodes disposed at different positions within the principalfluid flow chamber relative to the workpiece. After seed layer repair,additional metal is deposited in an electrolytic bulk plating processonto the enhanced seed layer, under conditions in which the depositionrate of the electrolytic deposition process is substantially greaterthan the deposition rate of the process used to repair the metal seedlayer.

Another embodiment of the invention provides a process for applying ametallization interconnect structure to a workpiece on which anultra-thin metal seed layer has been formed using a first depositionprocess. The first deposition process anchors the ultra-thin metal seedlayer to an underlying layer, the ultra-thin metal seed layer havingphysical characteristics that render it generally unsuitable for bulkelectrolytic deposition of a metal onto the metal seed layer. Theprocess entails repairing the ultra-thin metal seed layer byelectrochemically depositing additional metal on the ultra-thin metalseed layer within a principal fluid chamber of a reactor to provide anenhanced seed layer using a second deposition process, that is differentfrom the first deposition process. The second deposition process entailssupplying electroplating power to a plurality of electrodes within theprincipal fluid flow chamber. At least two of the plurality ofelectrodes are independently connected to an electrical power supply.The supply of electrical power to the at least two electrodes isindependently controlled during repair of the ultra-thin metal seedlayer. After repair of the seed layer, additional metal iselectrolytically deposited on the enhanced seed layer under conditionsin which the deposition rate of the electrolytic deposition process issubstantially greater than the deposition rate of the process used torepair the metal seed layer.

Another embodiment of the invention provides a process for applying ametallization interconnect structure to a workpiece on which anultra-thin metal seed layer has been formed using a first depositionprocess. The first deposition process anchors the ultra-thin metal seedlayer to an underlying layer, the ultra-thin metal seed layer havingphysical characteristics that render it generally unsuitable for bulkelectrolytic deposition of a metal onto the metal seed layer. Theprocess entails subjecting the workpiece to an electrochemicaldeposition process that is different from the first deposition process,in an alkaline electroplating bath. The alkaline electroplating bathincludes metal ions complexed with a complexing agent such thatadditional metal is deposited on the ultra-thin copper seed layer tothereby repair the seed layer. This results in an enhanced seed layer.The second deposition process is carried out by supplying electroplatingpower to a plurality of concentric anodes disposed at differentpositions, relative to the workpiece, within a principal fluid flowchamber of a reactor. Thereafter, additional metal is deposited on theenhanced seed layer using an electrolytic bulk deposition process underconditions in which the deposition rate of the electrolytic depositionprocess is substantially greater than the deposition rate of the processused to repair the metal seed layer.

Another embodiment of the invention provides a process for applying ametallization interconnect structure to a workpiece on which anultra-thin metal seed layer has been formed using a first depositionprocess. The first deposition process anchors the ultra-thin metal seedlayer to an underlying layer, the ultra-thin metal seed layer havingphysical characteristics that render it generally unsuitable for bulkelectrolytic deposition of a metal onto the metal seed layer. Theprocess entails subjecting the workpiece to an electrochemicaldeposition process that is different from the first deposition process,in an alkaline electroplating bath. The bath includes metal ionscomplexed with a complexing agent such that additional metal isdeposited on the ultra-thin copper seed layer to thereby repair the seedlayer, resulting in an enhanced seed layer. The first deposition processentails supplying electroplating power to a plurality of electrodeswithin the principal fluid flow chamber, wherein at least two of theplurality of electrodes are independently connected to an electricalpower supply. The supply of electrical power to the at least twoelectrodes is independently controlled during repair of the ultra-thinmetal seed layer. Thereafter additional metal is electrolyticallydeposited on the enhanced seed layer under conditions in which thedeposition rate of the electrolytic deposition process is substantiallygreater than the deposition rate of the process used to repair the metalseed layer.

Another embodiment of the invention provides a process for applying ametallization interconnect structure to a workpiece on which anultra-thin metal seed layer has been formed using a first depositionprocess. The first deposition process anchors the ultra-thin metal seedlayer to an underlying layer, the ultra-thin metal seed layer havingphysical characteristics that render it generally unsuitable for bulkelectrolytic deposition of a metal onto the metal seed layer. Theprocess entails repairing the ultra-thin metal seed layer byelectrochemically depositing additional metal on the ultra-thin metalseed layer within a principal fluid chamber of a reactor to provide anenhanced seed layer using a second deposition process, that is differentfrom the first deposition process. During repair, the workpiece isexposed to an electroplating solution within a fluid flow chamber of areactor. The fluid flow chamber defines a sidewall and a plurality ofnozzles disposed in the sidewall and arranged and directed to providevertical and radial fluid flow components that combine to create asubstantially uniform normal flow component radially across a surface ofthe workpiece on which the ultra-thin metal seed layer is formed.Thereafter, additional metal is electrolytically deposited on theenhanced seed layer under conditions in which the deposition rate of thedeposition process is substantially greater than the deposition rate ofthe process used to repair the metal seed layer.

Another embodiment of the invention provides a process for applying ametallization interconnect structure to a workpiece on which anultra-thin metal seed layer has been formed using a first depositionprocess. The first deposition process anchors the ultra-thin metal seedlayer to an underlying layer, the ultra-thin metal seed layer havingphysical characteristics that render it generally unsuitable for bulkelectrolytic deposition of a metal onto the metal seed layer. Theprocess entails subjecting the workpiece to an electrochemicaldeposition process that is different from the first deposition process,in an alkaline electroplating bath. The bath includes metal ionscomplexed with a complexing agent such that additional metal isdeposited on the ultra-thin copper seed layer to thereby repair the seedlayer, resulting in an enhanced seed layer. During repair, the workpieceis exposed to an electroplating solution within a fluid flow chamber ofa reactor, the fluid flow chamber defining a sidewall and a plurality ofnozzles disposed in the sidewall and arranged and directed to providevertical and radial fluid flow components that combine to create asubstantially uniform normal flow component radially across a surface ofthe workpiece on which the ultra-thin metal seed layer is formed.Thereafter, additional metal is deposited on the enhanced seed layerunder electrolytic plating conditions in which the deposition rate ofthe deposition process is substantially greater than the deposition rateof the process used to repair the metal seed layer.

Another embodiment of the invention provides a process for applying ametallization interconnect structure to a workpiece on which anultra-thin metal seed layer has been formed using a first deposition,process. The first deposition process anchors the ultra-thin metal seedlayer to an underlying layer, the ultra-thin metal seed layer havingphysical characteristics that render it generally unsuitable for bulkelectrolytic deposition of a metal onto the metal seed layer. Theprocess entails repairing the ultra-thin metal seed layer byelectrochemically depositing additional metal on the ultra-thin metalseed layer within a principal fluid chamber of a reactor to provide anenhanced seed layer using a second electrolytic or electrolessdeposition process, that is different from the first deposition process.Thereafter, additional metal is electrolytically deposited in bulk onthe enhanced seed layer under conditions in which the deposition rate ofthe electrolytic deposition process is substantially greater than thedeposition rate of the process used to repair the metal seed layer. Thebulk deposition process entails supplying electroplating power to aplurality of concentric anodes disposed at different positions withinthe principal fluid flow chamber relative to the workpiece.

Another embodiment of the invention provides a process for applying ametallization interconnect structure to a workpiece on which anultra-thin metal seed layer has been formed using a first depositionprocess. The first deposition process anchors the ultra-thin metal seedlayer to an underlying layer, the ultra-thin metal seed layer havingphysical characteristics that render it generally unsuitable for bulkelectrolytic deposition of a metal onto the metal seed layer. Theprocess entails repairing the ultra-thin metal seed layer byelectrolytically or electrolessly depositing additional metal on theultra-thin metal seed layer to provide an enhanced seed layer using asecond deposition process, that is different from the first depositionprocess. Thereafter, additional metal is electrolytically bulk depositedon the enhanced seed layer within a principal fluid chamber of a reactorunder conditions in which the deposition rate of the electrolyticdeposition process is substantially greater than the deposition rate ofthe process used to repair the metal seed layer. The bulk depositionentails supplying electroplating power to a plurality of electrodeswithin the principal fluid flow chamber, wherein at least two of theplurality of electrodes are independently connected to an electricalpower supply. The supply of electrical power to the at least twoelectrodes is independently controlled during deposition.

Another embodiment of the invention provides a process for applying ametallization interconnect structure to a workpiece on which anultra-thin metal seed layer has been formed using a first depositionprocess. The first deposition process anchors the ultra-thin metal seedlayer to an underlying layer, the ultra-thin metal seed layer havingphysical characteristics that render it generally unsuitable for bulkelectrolytic deposition of a metal onto the metal seed layer. Theprocess entails repairing the ultra-thin metal seed layer byelectrochemically depositing additional metal on the ultra-thin metalseed layer to provide an enhanced seed layer using a second depositionprocess, that is different from the first deposition process.Thereafter, additional metal is electrochemically bulk deposited on theenhanced seed layer within a principal fluid chamber of a reactor underconditions in which the deposition rate of the deposition process issubstantially greater than the deposition rate of the process used torepair the metal seed layer. The bulk deposition entails exposing theworkpiece to an electroplating solution within a fluid flow chamber of areactor, the fluid flow chamber defining a sidewall and a plurality ofnozzles disposed in the sidewall and arranged and directed to providevertical and radial fluid flow components that combine to create asubstantially uniform normal flow component radially across a surface ofthe workpiece on which the ultra-thin metal seed layer is formed.

The present invention employs a novel approach to the metallization of aworkpiece, such as a semiconductor workpiece. In accordance with theinvention, an alkaline electroplating bath is suitably used toelectroplate metal onto a seed layer, electroplate metal directly onto abarrier layer material, or repair (i.e., enhance) an ultra-thin copperseed layer which has been deposited on the barrier layer using adeposition process such as PVD or CVD. The metal deposition in thealkaline bath suitably takes place in a reactor including a plurality ofelectrodes. In a first embodiment the electrodes are concentric annularanodes arranged at differing positions relative to the workpiece. In asecond embodiment, the plurality of electrodes are independentlycontrolled for greater uniformity in metal deposition across theworkpiece. In a third embodiment, the reactor is configured to induce ahelical flow pattern in the plating bath solution during deposition.

The resulting metal layer provides an excellent conformal copper coatingthat fills trenches, vias, and other microstructures in the workpiece.When used for seed layer enhancement, the resulting metal seed layerprovides an excellent conformal metal coating that allows themicrostructures to be filled with a copper layer having good uniformityusing electrochemical deposition techniques. Further, metal layers thatare electroplated in the disclosed manner exhibit low sheet resistanceand are readily annealed at low temperatures.

The disclosed process, as noted above, is applicable to a wide range ofsteps used in the manufacture of a metallization layer in a workpiece.The workpiece may, for example, be a semiconductor workpiece that isprocessed to form integrated circuits or other microelectroniccomponents, or a micromechanical device. Without limitation as to theapplicability of the disclosed invention, a process for enhancing a seedlayer is described.

A process for applying a metallization interconnect structure to aworkpiece having a barrier layer deposited on a surface thereof is alsoset forth. The process includes the forming of an ultra-thin metal seedlayer on the barrier layer. The ultra-thin seed layer has a thickness ofless than or equal to about 500 Angstroms and may be formed from anymaterial that can serve as a seed layer for subsequent metal deposition.Such metals include, for example, copper, copper alloys, aluminum,aluminum alloys, nickel, nickel alloys, zinc, chromium, tin, gold,silver, lead, cadmium, platinum, palladium, iridium and ruthenium, etc.The ultra-thin seed layer is then enhanced or repaired by depositingadditional metal thereon in a separate deposition step to provide anenhanced seed layer that is suitable for use in a primary metaldeposition. The metal deposition in the alkaline bath suitably takesplace in a reactor including a plurality of electrodes. In a firstembodiment the electrodes are concentric annular anodes arranged atdiffering positions relative to the workpiece. In a second embodiment,the plurality of electrodes are independently controlled for greateruniformity in metal deposition across the workpiece. In a thirdembodiment, the reactor is configured to induce a helical flow patternin the plating bath solution during deposition. The enhanced seed layerhas a thickness at all points on sidewalls of substantially all recessedfeatures distributed within the workpiece that is equal to or greaterthan about 10% of the nominal seed layer thickness over an exteriorlydisposed surface of the workpiece.

In accordance with a specific embodiment of the process, acopper-containing metallization interconnect structure is formed. Tothis end, the ultra-thin seed layer is enhanced or repaired bysubjecting the semiconductor workpiece to an electrochemical copperdeposition process in which an alkaline bath having a complexing agentis employed. The copper complexing agent may be at least one complexingagent selected from a group consisting of EDTA, ED, and a polycarboxylicacid such as citric acid or salts thereof.

In an alternate embodiment, the seed layer may be enhanced by using anelectroless plating bath composition, such as an electroless coppersulfuric acid bath.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating an interconnect lineformed completely by PVD copper.

FIGS. 2A-2E are cross-sectional views through a semiconductor workpieceillustrating the various layers of material as they are applied inaccordance with one embodiment of the present invention.

FIG. 3 is a schematic representation of a first reactor suitable forenhancing an ultra-thin seed layer.

FIG. 4A is a graph illustrating the current-potential curves of aplating solution using a polycarboxylic acid, such as citric acid, as acomplexing agent.

FIG. 4B a graph illustrating the current-potential curves of a platingsolution using EDTA, an amine-containing plating solution, as thecomplexing agent.

FIG. 4C is a graph of sheet resistance change with annealing temperaturefor copper films deposited from a bath solution with and withoutammonium sulfate.

FIG. 4D is a graph illustrating plating solution conductivity as afunction of ethylene glycol concentration in collating solutions withand without ammonium sulfate.

FIG. 5 is a scanning electromicrograph photograph illustrating anultra-thin seed layer.

FIG. 6A is a scanning electromicrograph photograph illustrating anultra-thin seed layer that has been enhanced in a citric acid bath.

FIG. 6B is a scanning electromicrograph photograph illustrating anultra-thin seed layer that has been enhanced in an EDTA bath.

FIG. 7 is a schematic representation of a portion of a semiconductormanufacturing line suitable for implementing the disclosed seed layerenhancement steps.

FIG. 8 is a cross-sectional view of another embodiment of anelectroplating reactor assembly that may incorporate the presentinvention.

FIG. 9 is a schematic diagram of one embodiment of a reactor chamberthat may be used in the reactor assembly of FIG. 8 and includes anillustration of the velocity flow profiles associated with the flow ofprocessing fluid through the reactor chamber.

FIGS. 10A, 10B, 11 and 12 illustrate a specific construction of acomplete processing chamber assembly that has been specifically adaptedfor electrochemical processing of a semiconductor wafer and that hasbeen implemented to achieve the velocity flow profiles set forth in FIG.9.

FIGS. 13 and 14 illustrate a complete processing chamber assembly thathas been constructed in accordance with a further embodiment of thepresent invention.

FIGS. 15 and 16 are a cross-sectional views of illustrative velocityflow contours of the processing chamber embodiment of FIGS. 13 and 14.

FIGS. 17 and 18 are graphs illustrating the manner in which the anodeconfiguration of the processing chamber may be employed to achieveuniform plating.

FIGS. 19 and 20 illustrate a modified version of the processing chamberof FIGS. 13 and 14.

FIGS. 21 and 22 illustrate two embodiments of processing tools that mayincorporate one or more processing stations constructed in accordancewith the teachings of the present invention.

FIG. 23 is schematic block diagram of an electrochemical processingsystem constructed in accordance with one embodiment of the presentinvention.

FIG. 24 is a flowchart illustrating one manner in which the system ofFIG. 23 can use a predetermined set of sensitivity values to generate amore accurate electrical parameter set for use in meeting targetedphysical characteristics in the processing of a microelectronicworkpiece.

FIG. 25 is a graph of the change in electroplated film thickness perchange in current-time as a function of radial position on amicroelectronic workpiece for each of a plurality of individuallycontrolled anodes, such as those shown at A1-A4 of FIG. 23.

DETAILED DESCRIPTION OF THE INVENTION

The present invention employs a novel approach to applying coppermetallization to a workpiece, such as a semiconductor workpiece. Inaccordance with the invention, an alkaline electrolytic or electrolessbath containing a metal ion to be deposited, such as an alkalineelectrolytic copper bath, is used to electroplate metal onto a seedlayer, electroplate metal directly onto a barrier layer material, orenhance or repair an ultra-thin metal seed layer which has beendeposited on the barrier layer using a deposition process such as CVD orPVD. After enhancement of the ultra-thin metal seed layer, additionalmetal is suitable deposited, under differing conditions onto theenhanced seed layer, in a bulk fill process.

The present invention pertains to processes for applying a metallizationlayer. Although the disclosed method may be used in connection with asubstantial number of different metal compositions, the specificembodiment disclosed herein is directed to the application of acopper-containing metallization layer. To this end, an alkalineelectrolytic copper bath is used to enhance an ultra-thin copper seedlayer which has been deposited on a barrier layer using a depositionprocess such as PVD. The enhanced copper seed layer provides anexcellent conformal copper coating that allows trenches and vias to besubsequently bulk filled with a copper layer having good uniformityusing electrochemical deposition techniques.

The seed layer enhancement process, or the bulk fill process, or bothprocesses, are suitably carried out in a reactor that includes aplurality of anodes. The plurality of anodes may be arrangedconcentrically, or may be individually controlled with respect toapplied voltage potential or current, to effect the uniformity of metaldeposition across the workpiece. The seed layer enhancement and/or thebulk fill may also be carried out in a reactor that includes one or morejets, through which process fluid is introduced into a reaction chamber.The jets are angularly disposed relative to a chamber sidewall to createvertical and radial fluid flow components that combine to provide asubstantially uniform normal flow component radially across a surface ofthe workpiece on which the metal is deposited. These processes andreactors in which they are suitable carried out will be describedsubsequently herein below.

A cross-sectional view of a micro-structure, such as trench 5, that isto be filled with copper metallization is illustrated in FIG. 2A andwill be used to describe the seed layer enhancement aspects of thepresent invention. As shown, a thin barrier layer 10 of, for example,titanium nitride or tantalum nitride is deposited over the surface of asemiconductor device or, as illustrated in FIG. 2A, over a layer of adielectric 8, such as silicon dioxide. The barrier layer 10 acts toprevent the migration of copper to any semiconductor device formed inthe substrate. Any of the various known techniques, such as CVD or PVD,can be used to deposit the barrier layer depending on the particularbarrier material being used. Suitably, the thickness for the barrierlayer is approximately 100 to 300 Angstroms.

After the deposition of the barrier layer, an ultra-thin copper seedlayer 15 is deposited on the barrier layer 10. The resulting structureis illustrated in FIG. 2B. Suitably, the copper seed layer 15 is formedusing a vapor deposition technique, such as CVD or PVD. In order to haveadequate adhesion and copper coverage, a relatively thick (1000Angstroms) copper seed layer is usually required. Such a thick seedlayer leads to problems with close-off of small geometry trenches,however, when a PVD deposition process is employed for applying the seedlayer.

Contrary to traditional thoughts regarding seed layer application, thecopper seed layer 15 of the illustrated embodiment is ultra-thin, havinga thickness of about 50 to about 500 Angstroms, suitably about 100 toabout 250 Angstroms, and still more suitably about 200 Angstroms. Theultra-thin copper seed layer can be deposited using a CVD or a PVDprocess, or a combination of both. PVD is the preferred applicationprocess, however, because it can readily deposit copper on the barrierlayer 10 with relatively good adhesion. By depositing an ultra-thin seedlayer of copper, rather than the relatively thick seed layer used in theprior art, pinching off of the trenches can be avoided.

The use of an ultra-thin seed layer 15 generally introduces its own setof problems. One of the most significant of these problems is the factthat such ultra-thin layers do not generally coat the barrier layer 10in a uniform manner. Rather, voids or non-continuous seed layer regionson the sidewalls, such as at 20, are often present in an ultra-thin seedlayer 15 thereby resulting in the inability to properly apply asubsequent electrochemically deposited copper layer in the regions 20.Further, ultra-thin seed layers tend to include spikes, such as at 21,that impact the uniformity of the subsequent electrolytically depositedmetal layer. Such spikes 21 result in high potential regions at whichthe copper deposits at a higher rate than at other, more level regions.As such, the seed layer 15 is not fully suitable for the traditionalelectroplating techniques typically used after application of a seedlayer.

The present inventors have found that an ultra-thin seed layer can beemployed if it is combined with a subsequent electrochemical seed layerenhancement technique. In a first embodiment, the electrochemicalenhancement technique is an electroplating technique using an alkalineplating bath. An alternate embodiment of electrochemical deposition toenhance or repair an ultra-thin or otherwise incomplete or deficientseed layer uses an electroless plating bath. Electroless plating bathsare well known in the art, such as electroless copper sulfuric acidbaths, and are used in accordance with the present invention to depositadditional metal on the initial ultra-thin seed layer to repair orenhance the seed layer.

The preferred technique of electroplating in an alkaline bath to repairor enhance a seed layer will now be described. To this end, thesemiconductor workpiece is subject to a subsequent process step in whicha further amount of copper 18 is applied to the ultra-thin seed layer tothereby enhance the seed layer. A seed layer enhanced by the additionaldeposition of copper is illustrated in FIG. 2C. As shown in FIG. 2C, thevoid or non-continuous regions 20 of FIG. 2B have been filled therebyleaving substantially all of the barrier layer 10 covered with copper.

Suitably, the seed layer enhancement process continues until a sidewallstep coverage, i.e., the ratio of the seed layer thickness at the bottomsidewall regions 22 to the nominal thickness of the seed layer at theexteriorly disposed side 23 workpiece, achieves a value of at least 10%.More suitably, the sidewall step coverage is at least about 20%. Suchsidewall step coverage values are present in substantially all of therecessed structures of the semiconductor workpiece. It will berecognized, however, that certain recessed structures distributed withinthe semiconductor workpiece may not reach these sidewall step coveragevalues. For example, such structures disposed at the peripheral edges ofa semiconductor wafer may not reach these step coverage values.Similarly, defects or contaminants at the situs of certain recessedstructures may prevent them from reaching the desired coverage values.The nominal thickness of the enhanced seed layer at the exteriorlydisposed side of the workpiece is suitably in the range of 500 angstroms1600 angstroms.

Although the embodiment of the process disclosed herein is described inconnection with copper metallization, it is understood that the basicprinciple of the enhancement of an ultra-thin seed layer prior to thebulk deposition thereof can be applied to other metals or alloys thatare capable of being electroplated. Such metals include iron, nickel,cobalt, zinc, copper-zinc, nickel-iron, cobalt-iron, etc.

The embodiments disclosed above utilize depositing a metal, such ascopper, during seed layer enhancement. It should be understood thatalternately a metal alloy, such as a copper alloy may be applied. Thealloy is suitably selected to include an element or elements thatpreferentially locate at the interfaces between differing materials,which enhances anchorage of the materials, and also may lead to improvedelectromigration effect.

A thermal processing step may also be employed after seed layerenhancement deposition, at an elevated temperature selected to causematerial diffusion at the interfaces between materials, therebyanchoring the materials or components thereof together.

A schematic representation of a reactor 25 suitable for enhancing theultra-thin copper seed layer is illustrated in FIG. 3. It will berecognized that this apparatus is also suitable for applying a blanketplating layer and/or full-fill plating of recessed micro-structures. Asshown, a semiconductor workpiece, such as a semiconductor wafer 30, ispositioned face down in a bath 35 of electroplating solution. One ormore contacts 40 are provided to connect the wafer 30 to a plating powersupply 45 as a cathode of an electroplating cell. An anode 50 isdisposed in the bath 35 and is connected to the plating power supply 45.Suitably, a diffuser 55 is disposed between the anode 50 and thewafer/cathode 30. The wafer 30 may be rotated about axis 60 during theenhancement process. Anode 50 may be provided with a dielectric shield65 at a backside thereof which faces an incoming stream of plating bathfluid. Alternate and preferred reactors for use in the present inventionwill be described subsequently herein below.

A. Electroplating Solutions and Processes

As noted above, certain aspects of the present invention relate to newand useful plating solutions. These solutions can be used for blanketplating, full-fill of the recessed micro-structures, seed layerenhancement, etc. The preferred electrolytic bath solution for enhancingthe seed layer is an alkaline copper bath in which copper ions arecomplexed with a complexing agent. A suitable composition and range ofconcentrations for the various components of the plating bath includethe following:

1. Copper sulfate: 0.03M to 0.25M (suitably, 0.04);

2. Complexing agent: complex to metal ratios from 1 to 4, suitably 2;

3. Boric acid: 0.01M to 0.5M, suitably 0.05M; and

4. pH: 5-13, suitably 9.5.

A suitable source of copper ions is copper sulfate (CuSO₄). Theconcentration of copper sulfate in the bath is suitably within the rangeof 0.03 to 0.25 M, and is more suitably about 0.1 M.

Complexing agents that are suitable for use in the present inventionform a stable complex with copper ions and prevent the precipitation ofcopper hydroxide. Ethylene diamine tetracetic acid (EDTA), ethylenediamine (ED), citric acid, and their salts have been found to beparticularly suitable copper complexing agents. The molar ratio ofcomplexing agent to copper sulfate in the bath is suitably within therange of 1 to 4, and is suitably about 2. Such complexing agents can beused alone, in combination with one another, or in combination with oneor more further complexing agents.

The electrolytic bath is suitably maintained at a pH of at least 9.0.Potassium hydroxide, ammonium hydroxide, tetramethylammonium hydroxide,or sodium hydroxide is utilized to adjust and maintain the pH at thedesired level of 9.0 or above. A suitable pH for a citric acid or EDbath is about 9.5, while a suitable pH for an EDTA bath is about 12.5.As noted above, the complexing agent assists in preventing the copperfrom precipitating at the high pH level.

Additional components can be added to the alkaline copper bath. Forexample, boric acid (H₃BO₃) aids in maintaining the pH at 9.5 whencitric acid or ED is used as the complexing agent, and provides brightercopper deposits when added to an electrolytic bath containing EDTA asthe complexing agent. If boric acid is added, its concentration in thebath is suitably within the range of 0.01 to 0.5 M.

In general, the temperature of the bath can be within the range of 20 to35° C., with 25° C. being a suitable temperature. The current densityfor electrolytically depositing copper to enhance the copper seed layercan be 1 to 5 milliamps/cm², while a plating time of about 1 to about 5minutes is sufficient to enhance the copper seed layer. The platingwaveform may be, for example, a forward periodic pulse having a periodof 2 msec at a 50% duty cycle.

An amine free acid complexing agent, for example, a polycarboxylic acid,such as citric acid, and salts thereof, is preferable to the use of EDTAor ED. EDTA and ED include amine groups. These amine groups often remainon the surface of the semiconductor workpiece after rinsing and dryingof the wafer. Subsequent processes, particularly such processes asphotolithographic processes, may be corrupted by the reactions resultingfrom the presence of these amine groups. The amine groups may, forexample, interfere with the chemical reactions associated with thexposing and/or curing of photoresist materials. As such, amine freecomplexing agents are particularly suitable in processes in which aphotolithographic process follows an electrodeposition process.

A further advantage of using a polycarboxylic acid, such as citric acid,stems from the fact that the magnitude of the voltage potential at whichthe copper is plated is greater than the magnitude of the voltagepotential at which the copper is plated in a bath containing EDTA. Thisis illustrated in FIGS. 4A and 4B where FIG. 4A is a current-potentialgraph for a citric acid bath, and FIG. 4B is a current-potential graphfor an EDTA bath. Electroplating takes place at the voltage where thecorresponding current increases abruptly. This plating voltage isreferred to as the deposition potential, which is approximately −1.25volts as shown in FIG. 4A for a bath employing citric acid as thecomplexing agent, and is approximately −1.0 volts as shown in FIG. 4Bfor a bath employing EDTA as the complexing agent. The current peaks (7070′ for the a bath containing a citric acid, and 72, 72′ for the bathcontaining the EDTA) are the limiting currents which are mainlydetermined by mass transfer and the concentration of copper ions in theplating solutions. As illustrated, the magnitude of the current and theparticular plating potential is slightly dependent on the substratematerial. The different substrate results are illustrated in FIGS. 4Aand 4B, where 70 and 72 are the curves for a copper substrate material,and 70′ and 72′ are curves for a copper substrate material comprised ofcopper with a copper oxide coating. It is noted that additional peaksoccur on oxidized copper in the same electrolytes. These peaks arerelated to the electrochemical reduction of copper oxide to metalliccopper before the alkaline electrochemical copper deposition.

It is believed that a copper layer plated at a higher plating potentialin an alkaline bath provides greater adhesion to the underlying barrierlayer than a copper layer plated at a lower plating potential in an acidbath. For copper to adhere to the barrier material, it is thought thatcopper ions must impinge on the barrier surface with sufficient energyto penetrate a thin oxidized or contaminated layer at the barriersurface. It is therefore believed that a copper layer deposited at ahigher magnitude plating potential adhere is better to the exposedbarrier layer during the plating process when compared to a layer platedusing a smaller magnitude plating potential. This factor, combined withthe inter-copper chemical bond between the PVD copper and theelectrochemically deposited copper provides for an enhanced seed layerhaving excellent electrical as well as barrier adhesion properties. Suchcharacteristics are also desirable for films used in blanket plating,full-fill plating, pattern plating, etc.

It has been found that the resistivity of the deposited copper film isdirectly related to the resistivity of the plating bath solution.Additives that assist in lowering the resistivity of the solutiontherefore provide a corresponding reduction in the resistivity of thedeposited film.

Experimental results indicate that addition of ammonium sulfatesignificantly reduces the resistivity of the plating bath solution and,as such, the deposited film. The sheet resistance obtained for differentamounts of ammonium sulfate are compared in the graph FIG. 4C. As can beseen, the highest sheet resistance, either with or without annealing athigh temperatures, was obtained in the bath containing no ammoniumsulfate. If ammonium hydroxide was used to adjust pH in which a traceamount of ammonium sulfate is introduced to the bath, the sheetresistance was reduced from 76 to 23. As the concentration of ammoniumsulfate increased from 0.1 M to 0.5 M, the sheet resistance continuouslydecreased in a corresponding manner.

Although ammonium sulfate assists in reducing the sheet resistance ofthe deposited copper layer, experimental results indicate that itreduces the conformality of the resulting copper film. However, theaddition of ethylene glycol to the ammonium sulfate containing solutionsubstantially increases the conformality of the resulting deposit. FIG.4D illustrates the relationship between the concentration of ethyleneglycol and the conductivity of a plating solution containing 0.2M the ofammonium sulfate.

A suitable composition and range of concentrations for the variouscomponents of a plating bath having ammonium sulfate include thefollowing:

1. Copper sulfate: 0.03M to 0.5M (suitably, 0.25M);

2. Complexing agent: complex to metal ratios from 1 to 4, suitably 2using ED;

3. Ammonium sulfate: 0.01M to 0.5M, suitably 0.3M; and

4. Boric acid: 0.00 to 0.5M, suitably 0.2M.

As noted above, such a bath composition can be used for blanket plating,pattern plating, full-fill plating, and seed layer enhancement.

With reference again to the specific seed layer enhanced aspects of thepresent invention, the enhanced seed layer of FIG. 2C is suitable forsubsequent electrochemical copper deposition. This subsequent copperdeposition may take place in an alkaline bath within the apparatusemployed to enhance the seed layer. This may be followed by alow-temperature annealing process that assists in lowering theresistivity of the deposited copper. Such a low-temperature annealingprocess suitably takes place at a temperature below about the 250degrees Celsius and, more suitably, below about 100 degrees Celsius.When a low-K dielectric material is employed to isolate the copperstructures, the upper annealing temperature limit should be chosen to bebelow the degradation temperature of the dielectric material.

Although the foregoing alkaline bath compositions may be used for theentire electrochemical deposition process, subsequent copper depositionsuitably takes place in an acid environment where plating rates aresubstantially higher than corresponding rates associated with alkalineplating baths. To this end, the semiconductor workpiece is suitablytransferred to an apparatus wherein the workpiece is thoroughly rinsedwith deionized water and then transferred to an apparatus similar tothat of FIG. 3 wherein the plating bath is acidic. For example, onesuitable copper bath comprises 170 g/l H₂SO₄, 17 g/l copper and 70 ppmChloride ions with organic additives. The organic additives are notabsolutely necessary to the plating reaction. Rather, the organicadditives may be used to produce desired film characteristics andprovide better filling of the recessed structures on the wafer surface.The organic additives may include levelers, brighteners, wetting agentsand ductility enhancers. It is during this deposition process that thetrench 5 is substantially filled with a further layer ofelectrochemically deposited copper 22. The resulting filledcross-section is illustrated in FIG. 2D. After being filled in thismanner, the barrier layer and the copper layers disposed above thetrench are removed using any suitable process thereby leaving only thetrench 5 with the copper metallization and associated barrier materialas shown in FIG. 2E.

While electrolytic seed layer enhancement is an embodiment of thepresent invention, the ultra-thin seed layer can alternately be enhancedin accordance with the present invention using an electroless platingbath solution containing metal ions to be deposited. Electroless platingbaths are well know. The workpiece with ultra-thin seed layer isimmersed in the electroless bath, or electroless bath solution isotherwise applies to the workpiece, for a predetermined time periodsufficient to deposit additional metal ions to enhance the seed layer,rendering it suitable for metal deposition at a higher rate.

Use of an alkaline electrolytic bath to enhance the copper seed layerhas particular advantages over utilizing acid copper baths without seedlayer enhancement. After deposition of the PVD copper seed layer, thecopper seed layer is typically exposed to an oxygen-containingenvironment. Oxygen readily converts metallic copper to copper oxide. Ifan acid copper bath is used to plate copper onto the seed layer afterexposure of the seed layer to an oxygen containing environment, the acidcopper bath would dissolve copper oxide that had formed, resulting invoids in the seed layer and poor uniformity of the copper layerdeposited on the seed layer. Use of an alkaline copper bath inaccordance with the disclosed embodiment avoids the problem byadvantageously reducing any copper oxide at the surface of the seedlayer to metallic copper. Another advantage of the alkaline copper bathis that the plated copper has much better adhesion to the barrier layerthan that plated from an acid copper bath. Additional advantages of theseed layer enhancement aspects of the present invention can be seen fromthe following Example.

EXAMPLE 1 Comparison of Acid Copper Plating with and without Seed LayerEnhancement

Semiconductor wafers 1, 2 and 3 were each coated with a 200 Angstrom PVDcopper seed layer. In accordance with the present invention, wafers 1and 2 had seed layer enhancement from citric acid and EDTA baths,respectively, the compositions of which are set forth below:

Bath for Wafer 1: 0.1 M Cu SO₄+0.2 M Citric acid+0.05 M H₃BO₃ in D.I.water at pH 9.5, temperature 25° C.

Bath for Wafer 2: 0.1 M Cu SO₄+0.2 M EDTA acid +0.05 H₃BO₃ in D.I. waterat pH 12.5, temperature 25° C.

Wafer 3 did not have any seed layer enhancement.

The three wafers were then plated with a 1.5 micron copper layer from anacid copper bath under identical conditions. The following Tablecompares the uniformities, as deduced from sheet resistancemeasurements, of the three wafers after the deposition of a copper layerhaving a nominal thickness of 1.5 microns.

TABLE 1 Non-uniformity Enhancement Current Standard deviation Wafer BathDensity (%, 1σ) 1 Citrate 3 min. 7.321 at 2 mA/cm² 2 EDTA 3 min. 6.233at 2 mA/cm² 3 None 0 46.10

As can be seen from the results in Table 1 above, seed layer enhancementin accordance with the disclosed process provides excellent uniformity(6 to 7%) compared to that without seed layer enhancement (46%). This isconsistent with observations during visual examination of the waferafter 1.5 micron electroplated copper had been deposited. Such visualexamination of the wafer revealed the presence of defects at waferelectrode contact points on the wafer without seed layer enhancement.

FIGS. 5, 6A and 6B are photographs taken using a SEM. In FIG. 5, anultra-thin seed layer has been deposited on the surface of asemiconductor wafer, including micro-structures, such as trenches 85. Asshown, void regions are present at the lower corners of the trenches. InFIG. 6A, the seed layer has been enhanced in the manner described abovein a bath containing citric acid as the complexing agent. Thisenhancement resulted in a conformal copper seed layer that is verysuited for subsequent electrochemical deposition of coppermetallization.

FIG. 6B illustrates a seed layer that has been enhanced in a bathcontaining EDTA as the complexing agent. The resulting seed layerincludes larger grain sizes that project as spikes from the sidewalls ofthe trenches. These sidewall grain projections make subsequentelectrochemical deposition filling of the trenches more difficult sincethey localize a higher plating rate resulting in non-uniformity of thesubsequent electrochemical deposition. This effect is particularlynoticeable in recessed micro-structures having small dimensions. Assuch, a complexing agent such as citric acid is more preferable whenfilling small micro-structures. Results comparable for copper bathscontaining citric acid have also been achieved using ED as thecomplexing agent.

B. Electrodeposition System

FIG. 7 is a schematic representation of a portion of a semiconductormanufacturing line 90 suitable for implementing the foregoing processes.The line 90 includes a vapor deposition tool or tool set 95 and anelectrochemical copper deposition tool or tool set 100. Transfer ofwafers between the tools/tool sets 95 and 100 may be implementedmanually or through an automated transfer mechanism 105. Suitably,automated transfer mechanism 105 transfers workpieces in a pod orsimilar environment. Alternatively, the transfer mechanism 105 maytransfer wafers individually or in an open carrier through a cleanatmosphere joining the tools/tool sets.

In operation, vapor deposition tool/tool set 95 is utilized to apply anultra-thin copper seed layer over at least portions of semiconductorworkpieces that are processed on line 90. Suitably, this is done using aPVD application process. Workpieces with the ultra-thin seed layer arethen transferred to tool/tool set 100, either individually or inbatches, where they are subject to electrochemical seed layerenhancement at, for example, processing station 110. For electrolyticseed layer enhancement, processing station 110 may be constructed in themanner set forth in FIG. 3. For electroless enhancement, a similarprocessing station 110 will be utilized, but electrical contact is notmade with the workpiece and voltage is not applied. After enhancement iscompleted, the workpieces are subject to a full electrochemicaldeposition process in which copper metallization is applied to theworkpiece to a desired interconnect metallization thickness. This latterprocess may take place at station 110, but suitably occurs at furtherprocessing station 115 which deposits the copper metallization in thepresence of an acidic plating bath. Before transfer to station 115, theworkpiece is suitably rinsed in DI water at station 112. Transfer of thewafers between stations 110, 112, and 115 may be automated by a waferconveying system 120. The electrochemical deposition tool set 100 may beimplemented using, for example, an LT-210™ model or an Equinox™ modelplating tool available from Semitool, Inc., of Kalispell, Mont.

C. Suitable Reactor for Seed Layer Enhancement

With reference to FIG. 8, a first reactor assembly 120 forelectroplating a microelectronic workpiece 125, such as a semiconductorwafer, is shown. Generally stated, the reactor assembly 120 is comprisedof a reactor head 130 and a corresponding reactor base, shown generallyat 137 and described in substantial detail below, in which theelectroplating solution is disposed. The reactor of FIG. 8 can also beused to implement electrochemical processing operations other thanelectroplating (e.g., electropolishing, anodization, etc.), and alsoelectroless deposition processes.

The reactor head 130 of the electroplating reactor assembly maycomprised of a stationary assembly 170 and a rotor assembly 175. Rotorassembly 175 is configured to receive and carry an associatedmicroelectronic workpiece 125, position the microelectronic workpiece ina process-side down orientation within a container of reactor base 137,and to rotate or spin the workpiece while joining itselectrically-conductive surface in the plating circuit of the reactorassembly 120. The rotor assembly 175 includes one or more cathodecontacts (when used for electrolytic processing) that provideelectroplating power to the surface of the microelectronic workpiece. Inthe illustrated embodiment, a cathode contact assembly is showngenerally at 185 and is described in further detail below. It will berecognized, however, that backside contact may be implemented in lieu offront side contact when the substrate is conductive or when analternative electrically conductive path is provided between the backside of the microelectronic workpiece and the front side thereof.

The reactor head 130 is typically mounted on a lift/rotate apparatuswhich is configured to rotate the reactor head 130 from anupwardly-facing disposition in which it receives the microelectronicworkpiece to be plated, to a downwardly facing disposition in which thesurface of the microelectronic workpiece to be plated is positioned sothat it may be brought into contact with the electroplating solution inreactor base 137, either planar or at a given angle. A robotic arm,which suitably includes an end effector, is typically employed forplacing the microelectronic workpiece 125 in position on the rotorassembly 175, and for removing the plated microelectronic workpiece fromwithin the rotor assembly. The contact assembly 185 may be operatedbetween an open state that allows the microelectronic workpiece to beplaced on the rotor assembly 175, and a closed state that secures themicroelectronic workpiece to the rotor assembly and brings theelectrically conductive components of the contact assembly 185 intoelectrical engagement with the surface of the microelectronic workpiecethat is to be plated.

It will be recognized that other reactor assembly configurations may beused with the inventive aspects of the disclosed reactor chamber, theforegoing being merely illustrative.

FIG. 9 illustrates the basic construction of processing base 137 and acorresponding computer simulation of the flow velocity contour patternresulting from the processing container construction. As illustrated,the processing base 137 generally comprises a main fluid flow chamber505, an antechamber 510, a fluid inlet 515, a plenum 520, a flowdiffuser 525 separating the plenum 520 from the antechamber 510, and anozzle/slot assembly 530 separating the plenum 520 from the main chamber505. These components cooperate to provide a flow of electrochemicalprocessing fluid (here, of the electroplating solution) at themicroelectronic workpiece 125 that has a substantially radiallyindependent normal component. In the illustrated embodiment, theimpinging flow is centered about central axis 537 and possesses a nearlyuniform component normal to the surface of the microelectronic workpiece125. This results in a substantially uniform mass flux to themicroelectronic workpiece surface that, in turn, enables substantiallyuniform processing thereof, for example, when used to introduce analkaline bath solution for seed layer enhancement.

Notably, as will be clear from the description below, this desirableflow characteristic is achieved without the use of a diffuser disposedbetween the anode(s) and surface of the microelectronic workpiece thatis to be electrochemically processed (e.g., electroplated). As such, theanodes used in the electroplating reactor can be placed in closeproximity to the surface of the microelectronic workpiece to therebyprovide substantial control over local electrical field/current densityparameters used in the electroplating process. This substantial degreeof control over the electrical parameters allows the reactor to bereadily adapted to meet a wide range of electroplating requirements(e.g., seed layer thickness, seed layer type, electroplated material,electrolyte bath properties, etc.) without a corresponding change in thereactor hardware. Rather, adaptations can be implemented by altering theelectrical parameters used in the electroplating process through, forexample, software control of the power provided to the anodes, as shallbe described further herein below.

The reactor design thus effectively de-couples the fluid flow fromadjustments to the electric field. An advantage of this approach is thata chamber with nearly ideal flow for electroplating and otherelectrochemical processes (i.e., a design which provides a substantiallyuniform diffusion layer across the microelectronic workpiece) may bedesigned that will not be degraded when electroplating or otherelectrochemical process applications require significant changes to theelectric field.

The foregoing advantages can be more greatly appreciated through acomparison with the conventional prior art reactors. In suchconventional designs, the diffuser must be moved closer to the surfaceof the workpiece if the distance between the anode and the workpiecesurface is to be reduced. However, moving the diffuser closer to theworkpiece significantly alters the flow characteristics of theelectroplating fluid at the surface of the workpiece. More particularly,the close proximity between the diffuser and the surface of theworkpiece introduces a corresponding increase in the magnitude of thenormal components of the flow velocity at local areas 9. As such, theanode cannot be moved so that it is in close proximity to the surface ofthe microelectronic workpiece that is to be electroplated withoutintroducing substantial diffusion layer control problems and undesirablelocalized increases in the electrical field corresponding to the patternof apertures in the diffuser. Since the anode cannot be moved in closeproximity to the surface of the microelectronic workpiece, theadvantages associated with increased control of the electricalcharacteristics of the electrochemical process cannot be realized. Stillfurther, movement of the diffuser to a position in close proximity withthe microelectronic workpiece effectively generates a plurality ofvirtual anodes defined by the hole pattern of the diffuser. Given theclose proximity of these virtual anodes to the microelectronic workpiecesurface, the virtual anodes have a highly localized effect. This highlylocalized effect cannot generally be controlled with any degree ofaccuracy given that any such control is solely effected by varying thepower to the single, real anode. A substantially uniform electroplatedfilm is thus difficult to achieve with such a plurality of looselycontrolled virtual anodes.

With reference again to FIG. 9, electroplating solution is providedthrough inlet 515 disposed at the bottom of the base 137. The fluid fromthe inlet 515 is directed therefrom at a relatively high velocitythrough antechamber 510. In the illustrated embodiment, antechamber 510includes an acceleration channel 540 through which the electroplatingsolution flows radially from the fluid inlet 515 toward fluid flowregion 545 of antechamber 510. Fluid flow region 545 has a generallyinverted U-shaped cross-section that is substantially wider at itsoutlet region proximate flow diffuser 525 than at its inlet regionproximate channel 540. This variation in the cross-section assists inremoving any gas bubbles from the electroplating solution before theelectroplating solution is allowed to enter the main chamber 505. Gasbubbles that would otherwise enter the main chamber 505 are allowed toexit the processing base 137 through a gas outlet (not illustrated inFIG. 9, but illustrated in the embodiment shown in FIGS. 10-12) disposedat an upper portion of the antechamber 510.

Electroplating solution within antechamber 510 is ultimately supplied tomain chamber 505. To this end, the electroplating solution is firstdirected to flow from a relatively high-pressure region 550 of theantechamber 510 to the comparatively lower-pressure plenum 520 throughflow diffuser 525. Nozzle assembly 530 includes a plurality of nozzlesor slots 535 that are disposed at a slight angle with respect tohorizontal. Electroplating solution exits plenum 520 through nozzles 535with fluid velocity components in the vertical and radial directions.

Main chamber 505 is defined at its upper region by a contoured sidewall560 and a slanted sidewall 565. The contoured sidewall 560 assists inpreventing fluid flow separation as the electroplating solution exitsnozzles 535 (particularly the uppermost nozzle(s)) and turns upwardtoward the surface of microelectronic workpiece 125. Beyond breakpoint570, fluid flow separation will not substantially affect the uniformityof the normal flow. As such, sidewall 565 can generally have any shape,including a continuation of the shape of contoured sidewall 560. In thespecific embodiment disclosed here, sidewall 565 is slanted and, as willbe explained in further detail below, is used to support one or moreanodes.

Electroplating solution exits from main chamber 505 through a generallyannular outlet 572. Fluid exiting outlet 572 may be provided to afurther exterior chamber for disposal or may be replenished forre-circulation through the electroplating solution supply system.

The processing base 137 is also provided with one or more anodes. In theillustrated embodiment, a principal anode 580 is disposed in the lowerportion of the main chamber 505. If the peripheral edges of the surfaceof the microelectronic workpiece 125 extend radially beyond the extentof contoured sidewall 560, then the peripheral edges are electricallyshielded from principal anode 580 and reduced plating will take place inthose regions. As such, a plurality of annular anodes 585 are disposedin a generally concentric manner on slanted sidewall 565 to provide aflow of electroplating current to the peripheral regions.

Anodes 580 and 585 of the illustrated embodiment are disposed atdifferent distances from the surface of the microelectronic workpiece125 that is being electroplated. More particularly, the anodes 580 and585 are concentrically disposed in different horizontal planes. Such aconcentric arrangement combined with the vertical differences allow theanodes 580 and 585 to be effectively placed close to the surface of themicroelectronic workpiece 125 without generating a corresponding adverseimpact on the flow pattern as tailored by nozzles 535. The plurality ofanodes illustrated are arranged at increasing distances from theworkpiece from an innermost one of the concentric anodes to an outermostone of the concentric anodes. However, for differing depositionpatterns, an alternate arrangement providing for the distance from anodeto workpiece increasing from outermost to innermost is also within thescope of the present invention.

The effect and degree of control that an anode has on the electroplatingof microelectronic workpiece 125 is dependent on the effective distancebetween that anode and the surface of the microelectronic workpiece thatis being electroplated. More particularly, all other things being equal,an anode that is effectively spaced a given distance from the surface ofmicroelectronic workpiece 125 will have an impact on a larger area ofthe microelectronic workpiece surface than an anode that is effectivelyspaced from the surface of microelectronic workpiece 125 by a lesseramount. Anodes that are effectively spaced at a comparatively largedistance from the surface of microelectronic workpiece 125 thus haveless localized control over the electroplating process than do thosethat are spaced at a smaller distance. It is therefore desirable toeffectively locate the anodes in close proximity to the surface ofmicroelectronic workpiece 125 since this allows more versatile,localized control of the electroplating process. Advantage can be takenof this increased control to achieve greater uniformity of the resultingelectroplated film. Such control is exercised, for example, by placingthe electroplating power provided to the individual anodes under thecontrol of a programmable controller or the like, as shall be describedsubsequently herein below. Adjustments to the electroplating power canthus be made subject to software control based on manual or automatedinputs.

In the illustrated embodiment, anode 580 is effectively “seen” bymicroelectronic workpiece 125 as being positioned an approximatedistance Al from the surface of microelectronic workpiece 125. This isdue to the fact that the relationship between the anode 580 and sidewall560 creates a virtual anode having an effective area defined by theinnermost dimensions of sidewall 560. In contrast, anodes 585 areapproximately at effective distances A2, A3, and A4 proceeding from theinnermost anode to the outermost anode, with the outermost anode beingclosest to the microelectronic workpiece 125. All of the anodes 585 arein close proximity (i.e., about 25.4 mm or less, with the outermostanode being spaced from the microelectronic workpiece by about 10 mm) tothe surface of the microelectronic workpiece 125 that is beingelectroplated. Since anodes 585 are in close proximity to the surface ofthe microelectronic workpiece 125, they can be used to provideeffective, localized control over the radial film growth at peripheralportions of the microelectronic workpiece. Such localized control isparticularly desirable at the peripheral portions of the microelectronicworkpiece since it is those portions that are more likely to have a highuniformity gradient (most often due to the fact that electrical contactis made with the seed layer of the microelectronic workpiece at theoutermost peripheral regions resulting in higher plating rates at theperiphery of the microelectronic workpiece compared to the centralportions thereof).

The electroplating power provided to the foregoing anode arrangement canbe readily controlled to accommodate a wide range of platingrequirements without the need for a corresponding hardware modification.Some reasons for adjusting the electroplating power include changes tothe following:

seed layer thickness;

open area of plating surface (pattern wafers, edge exclusion);

final plated thickness;

plated film type (copper, platinum, seed layer enhancement);

bath conductivity, metal concentration; and

plating rate.

The foregoing anode arrangement is particularly well-suited for platingmicroelectronic workpieces having highly resistive seed layers, forenhancing such highly resistive seed layers, and also for plating highlyresistive materials on microelectronic workpieces. Generally stated, themore resistive the seed layer or material that is to be deposited, themore the magnitude of the current or potential at the central anode 580(or central anodes) should be increased to yield a uniform film. Thiseffect can be understood in connection with an example and the set ofcorresponding graphs set forth in FIGS. 17 and 18.

FIG. 17 is a graph of four different computer simulations reflecting thechange in growth of an electroplated film versus the radial positionacross the surface of a microelectronic workpiece. The graph illustratesthe changing growth that occurs when the current to a given one of thefour anodes 580, 585 is changed without a corresponding change in thecurrent to the remaining anodes. In this illustration, Anode 1corresponds to anode 580 and the remaining Anodes 2 through 4 correspondto anodes 585 proceeding from the interior most anode to the outermostanode. The peak plating for each anode occurs at a different radialposition. Further, as can be seen from this graph, anode 580, beingeffectively at the largest distance from the surface of the workpiece,has an effect over a substantial radial portion of the workpiece andthus has a broad affect over the surface area of the workpiece. Incontrast, the remaining anodes have substantially more localized effectsat the radial positions corresponding to the peaks of the graph of FIG.17.

The differential radial effectiveness of the anodes 580, 585 can beutilized to provide an effectively uniform electroplated film across thesurface of the microelectronic workpiece. To this end, each of theanodes 580, 585 may be provided with a fixed current that may differfrom the current provided to the remaining anodes. These plating currentdifferences can be provided to compensate for the increased plating thatgenerally occurs at the radial position of the workpiece surfaceproximate the contacts of the cathode contact assembly 185 (FIG. 8).

Likewise, the current to the individual anodes 580, 585 can be adjustedto provide a radially uniform deposition of metal during seed layerenhancement in accordance with the present invention, including duringseed layer enhancement in an electrolytic alkaline bath.

The computer simulated effect of a predetermined set of plating currentdifferences on the normalized thickness of the electroplated film as afunction of the radial position on the microelectronic workpiece overtime is shown in FIG. 18. In this simulation, the seed layer was assumedto be uniform at to. As illustrated, there is a substantial differencein the thickness over the radial position on the microelectronicworkpiece during the initial portion of the electroplating process. Thisis generally characteristic of workpieces having seed layers that arehighly resistive, such as those that are formed from a highly resistivematerial or that are very thin. However, as can be seen from FIG. 18,the differential plating that results from the differential currentprovided to the anodes 580, 585 forms a substantially uniform platedfilm by the end of the electroplating process. It will be recognizedthat the particular currents that are to be provided to anodes 580, 585depends upon numerous factors including, but not necessarily limited to,the desired thickness and material of the electroplated film, thethickness and material of the initial seed layer, the distances betweenanodes 580, 585 and the surface of the microelectronic workpiece,electrolyte bath properties, etc.

Anodes 580, 585 may be consumable, but are suitably inert and formedfrom platinized titanium or some other inert conductive material.However, as noted above, inert anodes tend to evolve gases that canimpair the uniformity of the plated film. To reduce this problem, aswell as to reduce the likelihood of the entry of bubbles into the mainprocessing chamber 505, processing base 37 includes several uniquefeatures. With respect to anode 580, a small fluid flow path forms aVenturi outlet 590 between the underside of anode 580 and the relativelylower pressure channel 540 (see FIG. 9). This results in a Venturieffect that causes the electroplating solution proximate the surfaces ofanode 580 to be drawn away and, further, provides a suction flow (orrecirculation flow) that affects the uniformity of the impinging flow atthe central portion of the surface of the microelectronic workpiece.

The Venturi flow path 590 may be shielded to prevent any large bubblesoriginating from outside the chamber from rising through region 590.Instead, such bubbles enter the bubble-trapping region of theantechamber 510.

Similarly, electroplating solution sweeps across the surfaces of anodes585 in a radial direction toward fluid outlet 572 to remove gas bubblesforming at their surfaces. Further, the radial components of the fluidflow at the surface of the microelectronic workpiece assist in sweepinggas bubbles therefrom.

There are numerous further processing advantages with respect to theillustrated flow through the reactor chamber. As illustrated, the flowthrough the nozzles 535 is directed away from the microelectronicworkpiece surface and, as such, there are no jets of fluid created todisturb the uniformity of the diffusion layer. Although the diffusionlayer may not be perfectly uniform, it will be substantially uniform,and any non-uniformity will be relatively gradual as a result. Further,the effect of any minor non-uniformity may be substantially reduced byrotating the microelectronic workpiece during processing. A furtheradvantage relates to the flow at the bottom of the main chamber 505 thatis produced by the Venturi outlet, which influences the flow at thecenterline thereof. The centerline flow velocity is otherwise difficultto implement and control. However, the strength of the Venturi flowprovides a non-intrusive design variable that may be used to affect thisaspect of the flow.

As is also evident from the foregoing reactor design, the flow that isnormal to the microelectronic workpiece has a slightly greater magnitudenear the center of the microelectronic workpiece and creates adome-shaped meniscus whenever the microelectronic workpiece is notpresent (i.e., before the microelectronic workpiece is lowered into thefluid). The dome-shaped meniscus assists in minimizing bubble entrapmentas the microelectronic workpiece or other workpiece is lowered into theprocessing solution (here, the electroplating solution).

A still further advantage of the foregoing reactor design is that itassists in preventing bubbles that find their way to the chamber inletfrom reaching the microelectronic workpiece. To this end, the flowpattern is such that the solution travels downward just before enteringthe main chamber. As such, bubbles remain in the antechamber and escapethrough holes at the top thereof. Further, the upward sloping inlet path(see FIG. 12 and appertaining description) to the antechamber preventsbubbles from entering the main chamber through the Venturi flow path.

FIGS. 10-12 illustrate a specific construction of a complete processingchamber assembly 610 that has been specifically adapted forelectrochemical processing of a semiconductor microelectronic workpiece.More particularly, the illustrated embodiment is specifically adaptedfor depositing a uniform layer of material on the surface of theworkpiece using electroplating.

As illustrated, the processing base 137 shown in FIG. 8 is comprised ofprocessing chamber assembly 610 along with a corresponding exterior cup605. Processing chamber assembly 610 is disposed within exterior cup 605to allow exterior cup 605 to receive spent processing fluid thatoverflows from the processing chamber assembly 610. A flange 615 extendsabout the assembly 610 for securement with, for example, the frame ofthe corresponding tool.

With particular reference to FIGS. 11 and 12, the flange of the exteriorcup 605 is formed to engage or otherwise accept rotor assembly 75 ofreactor head 30 (shown in FIG. 8) and allow contact between themicroelectronic workpiece 25 and the processing solution, such aselectroplating solution, in the main fluid flow chamber 505. Theexterior cup 605 also includes a main cylindrical housing 625 into whicha drain cup member 627 is disposed. The drain cup member 627 includes anouter surface having channels 629 that, together with the interior wallof main cylindrical housing 625, form one or more helical flow chambers640 that serve as an outlet for the processing solution. Processingfluid overflowing a weir member 739 at the top of processing cup 35drains through the helical flow chambers 640 and exits an outlet (notillustrated) where it is either disposed of or replenished andre-circulated. This configuration is particularly suitable for systemsthat include fluid re-circulation since it assists in reducing themixing of gases with the processing solution thereby further reducingthe likelihood that gas bubbles will interfere with the uniformity ofthe diffusion layer at the workpiece surface.

In the illustrated embodiment, antechamber 510 is defined by the wallsof a plurality of separate components. More particularly, antechamber510 is defined by the interior walls of drain cup member 627, an anodesupport member 697, the interior and exterior walls of a mid-chambermember 690, and the exterior walls of flow diffuser 525.

FIGS. 10B and 11 illustrate the manner in which the foregoing componentsare brought together to form the reactor. To this end, the mid-chambermember 690 is disposed interior of the drain cup member 627 and includesa plurality of leg supports 692 that sit upon a bottom wall thereof. Theanode support member 697 includes an outer wall that engages a flangethat is disposed about the interior of drain cup member 627. The anodesupport member 697 also includes a channel 705 that sits upon andengages an upper portion of flow diffuser 525, and a further channel 710that sits upon and engages an upper rim of nozzle assembly 530.Mid-chamber member 690 also includes a centrally disposed receptacle 715that is dimensioned to accept the lower portion of nozzle assembly 530.Likewise, an annular channel 725 is disposed radially exterior of theannular receptacle 715 to engage a lower portion of flow diffuser 525.

In the illustrated embodiment, the flow diffuser 525 is formed as asingle piece and includes a plurality of vertically oriented slots 670.Similarly, the nozzle assembly 530 is formed as a single piece andincludes a plurality of horizontally oriented slots that constitute thenozzles 535.

The anode support member 697 includes a plurality of annular groovesthat are dimensioned to accept corresponding annular anode assemblies785. Each anode assembly 785 includes an anode 585 (suitably formed fromplatinized titanium or another inert metal) and a conduit 730 extendingfrom a central portion of the anode 585 through which a metal conductormay be disposed to electrically connect the anode 585 of each assembly785 to an external source of electrical power. Conduit 730 is shown toextend entirely through the processing chamber assembly 610 and issecured at the bottom thereof by a respective fitting 733. In thismanner, anode assemblies 785 effectively urge the anode support member697 downward to clamp the flow diffuser 525, nozzle assembly 530,mid-chamber member 690, and drain cup member 627 against the bottomportion 737 of the exterior cup 605. This allows for easy assembly anddisassembly of the processing chamber 610. However, it will berecognized that other means may be used to secure the chamber elementstogether as well as to conduct the necessary electrical power to theanodes.

The illustrated embodiment also includes a weir member 739 thatdetachably snaps or otherwise easily secures to the upper exteriorportion of anode support member 697. As shown, weir member 739 includesa rim 742 that forms a weir over which the processing solution flowsinto the helical flow chamber 640. Weir member 739 also includes atransversely extending flange 744 that extends radially inward and formsan electric field shield over all or portions of one or more of theanodes 585. Since the weir member 739 may be easily removed andreplaced, the processing chamber assembly 610 may be readilyreconfigured and adapted to provide different electric field shapes.Such differing electrical field shapes are particularly useful in thoseinstances in which the reactor must be configured to process more thanone size or shape of a workpiece. Additionally, this allows the reactorto be configured to accommodate workpieces that are of the same size,but have different plating area requirements.

The anode support member 697, with the anodes 585 in place, forms thecontoured sidewall 560 and slanted sidewall 565 that is illustrated inFIG. 9. As noted above, the lower region of anode support member 697 iscontoured to define the upper interior wall of antechamber 510 andsuitably includes one or more gas outlets 665 that are disposedtherethrough to allow gas bubbles to exit from the antechamber 510 tothe exterior environment.

With particular reference to FIG. 12, fluid inlet 515 is defined by aninlet fluid guide, shown generally at 810, that is secured to the floorof mid-chamber member 690 by one or more fasteners 815. Inlet fluidguide 810 includes a plurality of open channels 817 that guide fluidreceived at fluid inlet 515 to an area beneath mid-chamber member 690.Channels 817 of the illustrated embodiment are defined by upwardlyangled walls 819. Processing fluid exiting channels 817 flows therefromto one or more further channels 821 that are likewise defined by wallsthat angle upward.

Central anode 580 includes an electrical connection rod 581 thatproceeds to the exterior of the processing chamber assembly 610 throughcentral apertures formed in nozzle assembly 530, mid-chamber member 690and-inlet fluid guide 810. The small Venturi flow path regions shown at590 in FIG. 9 are formed in FIG. 12 by vertical channels 823 thatproceed through drain cup member 690 and the bottom wall of nozzlemember 530. As illustrated, the fluid inlet guide 810 and, specifically,the upwardly angled walls 819 extend radially beyond the shieldedvertical channels 823 so that any bubbles entering the inlet proceedthrough the upward channels 821 rather than through the verticalchannels 823.

FIGS. 13-16 illustrate a further embodiment of an improved reactorchamber. The embodiment illustrated in these figures retains theadvantageous electric field and flow characteristics of the foregoingreactor construction while concurrently being useful for situations inwhich anode/electrode isolation is desirable. Such situations include,but are not limited to, the following:

instances in which the electrochemical electroplating solution must passover an electrode, such as an anode, at a high flow rate to be optimallyeffective;

instances in which one or more gases evolving from the electrochemicalreactions at the anode surface must be removed in order to insureuniform electrochemical processing; and

instances in which consumable electrodes are used.

With reference to FIGS. 13 and 14, the reactor includes anelectrochemical electroplating solution flow path into the innermostportion of the processing chamber that is very similar to the flow pathof the embodiment illustrated in FIG. 9 and as implemented in theembodiment of the reactor chamber shown in FIGS. 10A through 12. Assuch, components that have similar functions are not further identifiedhere for the sake of simplicity. Rather, only those portions of thereactor that significantly differ from the foregoing embodiment areidentified and described below.

A significant distinction between the embodiments exists, however, inconnection with the anode electrodes and the appertaining structures andfluid flow paths. More particularly, the reactor based 137 includes aplurality of ring-shaped anodes 1015, 1020, 1025 and 1030 that areconcentrically disposed with respect to one another in respective anodechamber housings 1017, 1022, 1027 and 1032. As shown, each anode 1015,1020, 1025 and 1030 has a vertically oriented surface area that isgreater than the surface area of the corresponding anodes shown in theforegoing embodiments. Four such anodes are employed in the disclosedembodiment, but a larger or smaller number of anodes may be useddepending upon the electrochemical processing parameters and resultsthat are desired. Each anode 1015, 1020, 1025 and 1030 is supported inthe respective anode chamber housing 1017, 1022, 1027 and 1032 by atleast one corresponding support/conductive member 1050 that extendsthrough the bottom of the processing base 137 and terminates at anelectrical connector 1055 for connection to an electrical power source.

In accordance with the disclosed embodiment, fluid flow to and throughthe three outer most chamber housings 1022, 1027 and 1032 is providedfrom an inlet 1060 that is separate from inlet 515, which supplies thefluid flow through an innermost chamber housing 1017. As shown, fluidinlet 1060 provides electroplating solution to a manifold 1065 having aplurality of slots 1070 disposed in its exterior wall. Slots 1070 are influid communication with a plenum 1075 that includes a plurality ofopenings 1080 through which the electroplating solution respectivelyenters the three anode chamber housings 1022, 1027 and 1032. Fluidentering the anode chamber housings 1017, 1022, 1027 and 1032 flows overat least one vertical surface and, suitably, both vertical surfaces ofthe respective anode 1015, 1020, 1025 and 1030.

Each anode chamber housing 1017, 1022, 1027 and 1032 includes an upperoutlet region that opens to a respective cup 1085. Cups 1085, asillustrated, are disposed in the reactor chamber so that they areconcentric with one another. Each cup includes an upper rim 1090 thatterminates at a predetermined height with respect to the other rims,with the rim of each cup terminating at a height that is verticallybelow the immediately adjacent outer concentric cup. Each of the threeinnermost cups further includes a substantially vertical exterior wall1095 and a slanted interior wall 1200. This wall construction creates aflow region 1205 in the interstitial region between concentricallydisposed cups (excepting the innermost cup that has a contoured interiorwall that defines the fluid flow region 1205 and then the outer mostflow region 1205 associated with the outer most anode) that increases inarea as the fluid flows upward toward the surface of the microelectronicworkpiece under process. The increase in area effectively reduces thefluid flow velocity along the vertical fluid flow path, with thevelocity being greater at a lower portion of the flow region 1205 whencompared to the velocity of the fluid flow at the upper portion of theparticular flow region.

The interstitial region between the rims of concentrically adjacent cupseffectively defines the size and shape of each of a plurality of virtualanodes, each virtual anode being respectively associated with acorresponding anode disposed in its respective anode chamber housing.The size and shape of each virtual anode that is seen by themicroelectronic workpiece under process is generally independent of thesize and shape of the corresponding actual anode. As such, consumableanodes that vary in size and shape over time as they are used can beemployed for anodes 1015, 1020, 1025 and 1030 without a correspondingchange in the overall anode configuration is seen by the microelectronicworkpiece under process. Further, given the deceleration experienced bythe fluid flow as it proceeds vertically through flow regions 1205, ahigh fluid flow velocity may be introduced across the vertical surfacesof the anodes 1015, 1020, 1025 and 1030 in the anode chamber housings1022, 1027 and 1032 while concurrently producing a very uniform fluidflow pattern radially across the surface of the microelectronicworkpiece under process. Such a high fluid flow velocity across thevertical surfaces of the anodes 1015, 1020, 1025 and 1030, as notedabove, is desirable when using certain Liz electrochemicalelectroplating solutions, such as electroplating fluids available fromAtotech. Further, such high fluid flow velocities may be used to assistin removing some of the gas bubbles that form at the surface of theanodes, particularly inert anodes. To this end, each of the anodechamber housings 1017, 1022, 1027 and 1032 may be provided with one ormore gas outlets (not illustrated) at the upper portion thereof to ventsuch gases.

Of further note, unlike the foregoing embodiment, element 1210 is asecurement that is formed from a dielectric material. The securement1210 is used to clamp a plurality of the structures forming reactor base137 together. Although securement 1210 may be formed from a conductivematerial so that it may function as an anode, the innermost anode seenby the microelectronic workpiece under process is suitably a virtualanode corresponding to the interior most anode 1015.

FIGS. 15 and 16 illustrate computer simulations of fluid flow velocitycontours of a reactor constructed in accordance with the embodimentshown in FIGS. 17 through 19. In this embodiment, all of the anodes ofthe reactor base may be isolated from a flow of fluid through the anodechamber housings. To this end, FIG. 15 illustrates the fluid flowvelocity contours that occur when a flow of electroplating solution isprovided through each of the anode chamber housings, while FIG. 16illustrates the fluid flow velocity contours that occur when there is noflow of electroplating solution provided through the anode chamberhousings past the anodes. This latter condition can be accomplished inthe reactor of by turning off the flow from the second fluid flow inlet(described below) and may likewise be accomplished in the reactor ofFIGS. 13 and 14 by turning of the fluid flow through inlet 1060. Such acondition may be desirable in those instances in which a flow ofelectroplating solution across the surface of the anodes is found tosignificantly reduce the organic additive concentration of the solution.

FIG. 19 illustrates a variation of the reactor embodiment shown in FIG.14. For the sake of simplicity, only the elements pertinent to thefollowing discussion are provided with reference numerals.

This further embodiment employs a different structure for providingfluid flow to the anodes 1015, 1020, 1025 and 1030. More particularly,the further embodiment employs an inlet member 2010 that serves as aninlet for the supply and distribution of the processing fluid to theanode chamber housings 1017, 1022, 1027 and 1032.

With reference to FIGS. 19 and 20, the inlet member 2010 includes ahollow stem 2015 that may be used to provide a flow of electroplatingfluid. The hollow stem 2015 terminates at a stepped hub 2020. Steppedhub 2020 includes a plurality of steps 2025 that each include a groovedimensioned to receive and support a corresponding wall of the anodechamber housings. Processing fluid is directed into the anode chamberhousings through a plurality of channels 2030 that proceed from amanifold area into the respective anode chamber housing.

This latter inlet arrangement assists in further electrically isolatinganodes 1015, 1020, 1025 and 1030 from one another. Such electricalisolation occurs due to the increased resistance of the electrical flowpath between the anodes. The increased resistance is a direct result ofthe increased length of the fluid flow paths that exist between theanode chamber housings.

The manner in which the electroplating power is supplied to themicroelectronic workpiece at the peripheral edge thereof effects theoverall film quality of the deposited metal. Some of the more desirablecharacteristics of a contact assembly used to provide suchelectroplating power include, for example, the following:

uniform distribution of electroplating power about the periphery of themicroelectronic workpiece to maximize the uniformity of the depositedfilm;

consistent contact characteristics to insure wafer-to-wafer uniformity;

minimal intrusion of the contact assembly on the microelectronicworkpiece periphery to maximize the available area for deviceproduction; and

minimal plating on the barrier layer about the microelectronic workpieceperiphery to inhibit peeling and/or flaking.

To meet one or more of the foregoing characteristics, reactor assembly120 suitably employs a contact assembly 185 that provides either acontinuous electrical contact or a high number of discrete electricalcontacts with the microelectronic workpiece 125. By providing a morecontinuous contact with the outer peripheral edges of themicroelectronic workpiece 125, in this case around the outercircumference of the semiconductor wafer, a more uniform current issupplied to the microelectronic workpiece 125 that promotes more uniformcurrent densities. The more uniform current densities enhance uniformityin the depth of the deposited material.

Contact assembly 185, in accordance with an embodiment, includes contactmembers that provide minimal intrusion about the microelectronicworkpiece periphery while concurrently providing consistent contact withthe seed layer. Contact with the seed layer is enhanced by using acontact member structure that provides a wiping action against the seedlayer as the microelectronic workpiece is brought into engagement withthe contact assembly. This wiping action assists in removing any oxidesat the seed layer surface thereby enhancing the electrical contactbetween the contact structure and the seed layer. As a result,uniformity of the current densities about the microelectronic workpieceperiphery are increased and the resulting film is more uniform. Further,such consistency in the electrical contact facilitates greaterconsistency in the electroplating process from wafer-to-wafer therebyincreasing wafer-to-wafer uniformity.

Contact assembly 185, as will be set forth in further detail below, alsosuitably includes one or more structures that provide a barrier,individually or in cooperation with other structures, that separates thecontact/contacts, the peripheral edge portions and backside of themicroelectronic workpiece 125 from the plating solution. This preventsthe plating of metal onto the individual contacts and, further, assistsin preventing any exposed portions of the barrier layer near the edge ofthe microelectronic workpiece 125 from being exposed to theelectroplating environment. As a result, plating of the barrier layerand the appertaining potential for contamination due to flaking of anyloosely adhered electroplated material is substantially limited.Exemplary contact assemblies suitable for use in the present system areillustrated in U.S. Ser. No. 09/113,723, filed Jul. 10, 1998, which ishereby incorporated by reference.

One or more of the foregoing reactor assemblies may be readilyintegrated in a processing tool that is capable of executing a pluralityof processes on a workpiece, such as a semiconductor microelectronicworkpiece. One such processing tool is the LT-210™ electroplatingapparatus available from Semitool, Inc., of Kalispell, Mont. FIGS. 21and 22 illustrate such integration.

The system of FIG. 21 includes a plurality of processing stations 1610.Suitably, these processing stations include one or more rinsing/dryingstations and one or more electroplating stations (including one or moreelectroplating reactors such as the one above), although furtherimmersion-chemical processing stations constructed in accordance withthe of the present invention may also be employed. The system alsosuitably includes a thermal processing station, such as at 1615, thatincludes at least one thermal reactor that is adapted for rapid thermalprocessing (RTP).

The workpieces are transferred between the processing stations 1610 andthe RTP station 1615 using one or more robotic transfer mechanisms 1620that are disposed for linear movement along a central track 1625. One ormore of the stations 1610 may also incorporate structures that areadapted for executing an in-situ rinse. Suitably, all of the processingstations as well as the robotic transfer mechanisms are disposed in acabinet that is provided with filtered air at a positive pressure tothereby limit airborne contaminants that may reduce the effectiveness ofthe microelectronic workpiece processing.

FIG. 22 illustrates a further embodiment of a processing tool in whichan RTP station 1635, located in portion 1630, that includes at least onethermal reactor, may be integrated in a tool set. Unlike the embodimentof FIG. 21, in this embodiment, at least one thermal reactor is servicedby a dedicated robotic mechanism 1640. The dedicated robotic mechanism1640 accepts workpieces that are transferred to it by the robotictransfer mechanisms 1620. Transfer may take place through anintermediate staging door/area 1645. As such, it becomes possible tohygienically separate the RTP portion 1630 of the processing tool fromother portions of the tool. Additionally, using such a construction, theillustrated annealing station may be implemented as a separate modulethat is attached to upgrade an existing tool set. It will be recognizedthat other types of processing stations may be located in portion 1630in addition to or instead of RTP station 1635.

D. Selective Electrode Control

The selective control and adjustment of the anodes for uniformelectrodeposition, such as during electrochemical deposition ofmetallization structures or seed layer enhancement, will now be furtherdescribed. FIG. 23 shows a schematic representation of the reactorassembly 120 illustrated in FIG. 8. Thus, as previously described, thereactor includes a reactor head 130 and a reactor base 137.

As previously described with reference to FIG. 9, the reactor head 130includes a stationary assembly and a rotor assembly that carries theworkpiece 125 and suitably positions it process-side down. The rotorassembly rotates or spins the workpiece 125 while joining itselectrically conductive surface. The reactor head 130 thus includes oneor more cathode contacts, shown generally at 185, that electricallycontact the lower surface of the workpiece 125.

The reactor base 137 includes an outer overflow container 1710 and aninterior processing container 1712. A flow of electroplating fluid isprovided to the processing container 1712 through the inlet 1714. Theelectroplating fluid fills the interior of processing container 1712 andoverflows a weir 1716 formed at the top of processing container. 1712.The fluid overflowing weir 1716 then enters overflow container 1710, andexits the reactor 120 through an outlet 1718. Outlet 1718 may bedirected to a recirculation system, chemical refurbishment system, ordisposal system.

An electrode assembly, shown generally at 1750, is disposed in theprocessing container 1712 in contact with the electrochemical processingfluid (here, the electroplating fluid). Electrode assembly 1750 includesa base member 1752 in which a plurality of fluid flow apertures 1754 aredisposed. The fluid flow apertures 1754 assist in disbursing theelectroplating fluid flow entering inlet 1714 so that the flow ofelectroplating fluid at the surface of microelectronic workpiece 125 isless localized and radially more uniform. Electrode assembly 1750 alsoincludes an electrode array, shown generally at 1756, that comprises aplurality of individual electrodes 1758 that are supported by basemember 1752. Electrode array 1756 may take on any number of physicalconfigurations. The particular physical configuration that is utilizedin a given reactor is principally dependent on the particular type andshape of microelectronic workpiece 125 that is to be processed. In theillustrated embodiment, microelectronic workpiece 125 is in the form ofa disk-shaped semiconductor wafer. Accordingly, the present inventorshave found that the individual electrodes 1758 may be formed as rings ofdifferent diameters and that they may be arranged concentrically inalignment with the center of microelectronic workpiece 125. It will berecognized, however, that other electrode array configurations may alsobe employed without departing from the scope of the present invention.

When reactor 120 is used to electroplate at least one surface ofmicroelectronic workpiece 125, the surface of the workpiece 125 that iselectroplated functions as a cathode in the electrochemical reactionwhile electrode array 1756 functions as an anode. To this end, thesurface of workpiece 125 that is to be electroplated is connected to anegative potential terminal of a power supply 1760 through contacts 185and the individual electrodes 1758 of electrode array 1756 are connectedto positive potential terminals of supply 1760. And the illustratedembodiment, each of the individual electrodes 1758 is connected to adiscrete terminal of supply 1760 so that supply 1760 may individuallyalter one or more electrical parameters, such as the current flow,associated with each of the individual electrodes 1758. As such, each ofthe individual electrodes 1758 of FIG. 23 is an individuallycontrollable electrode. It will be recognized, however, that one or moreof the individual electrodes 1758 of electrode array 1756 may beconnected to a common node/terminal of power supply 1760. In suchinstances, power supply 1760 will alter the one or more electricalparameters of the commonly connected electrodes 1758 concurrently, asopposed to individually, thereby effectively making the commonlyconnected electrodes 1758 a single, individually controllable electrode.As such, individually controllable electrodes can be formed fromphysically distinct electrodes that are connected to discrete terminalsof power supply 1760 as well as from physically distinct electrodes thatare commonly connected to a single discrete terminal of power supply1760. Electrode array 1756 suitably comprises at least two individuallycontrollable electrodes.

Electrode array 1756 and power supply 1760 facilitate localized controlof the electrical parameters used to electrochemically process themicroelectronic workpiece 125. This localized control of the electricalparameters can be used to provide greater uniformity of theelectrochemical processing across the surface of the microelectronicworkpiece when compared to a single electrode system. However,determining the electrical parameters for each of the electrodes 1758 inarray 1756 to achieve the desired process uniformity can be problematic.Accordingly, the present inventors have developed a method and apparatusthat simplifies and substantially automates the determination of theelectrical parameters associated with each of the individuallycontrollable electrodes. In accordance with this approach, a pluralityof sensitivity values are determined, either experimentally or throughnumerical simulation, and subsequently used to adjust the electricalparameters associated with each of the individually controllableelectrodes. The sensitivity values may be placed in a table or may be inthe form of a Jacobian matrix. This table/matrix holds informationcorresponding to process parameter changes (i.e., thickness of theelectroplated film) at various points on the workpiece 125 due toelectrical parameter perturbations (i.e., electrical current changes) toeach of the individually controllable electrodes. This table/matrix isderived from data from a baseline workpiece plus data from separate runswith a perturbation of a controllable electrical parameter to each ofthe individually controllable.

Once the values for the sensitivity table/matrix have been determined,the values may be stored in and used by control system 1765 to controlone or more of the electrical parameters that power supply 1760 uses inconnection with each of the individually controllable electrodes 1758.FIG. 24 is an exemplary flow diagram illustrating one manner in whichthe sensitivity table/matrix may be used to calculate an electricalparameter (i.e., current) for each of the individually controllableelectrodes 1758 that may be used to meet a target process parameter(i.e., target thickness of the electroplated film).

In the exemplary process of FIG. 24, control system 1765 utilizes twosets of input parameters along with the sensitivity table/matrix tocalculate the required electrical parameters. A first set of inputparameters corresponds to the data derived from a test run of theprocess while using a known, predetermined set of electrical parameters.This first set of input parameters can be derived by first executing atest run on a test workpiece using the predetermined electricalparameter set, as shown at step 1770. For example, a test run can beperformed by subjecting a microelectronic workpiece 125 to anelectroplating process in which the current provided to each of theindividually controllable electrodes 1758 is fixed at a predeterminedmagnitude for a given period of time.

After the test run is complete, the physical characteristics (i.e.,thickness of the electroplated film) of the test workpiece are measured,as at step 1772, and compared against a second set of input parametersat step 1774. In the illustrated embodiment of the method, the secondset of input parameters corresponds to the target physicalcharacteristics of the microelectronic workpiece that are to beultimately achieved by the process (i.e., the thickness of theelectroplated film). Notably, the target physical characteristics caneither be uniform over the surface of the microelectronic workpiece 125or vary over the surface. For example, in the illustrated embodiment,the thickness of an electroplated film on the surface of themicroelectronic workpiece 125 can be used as the target physicalcharacteristic, and the user may expressly specify the targetthicknesses at various radial distances from the center of theworkpiece.

The first and second set of input parameters are used at step 1774 togenerate a set of process error values. To ensure the integrity of thedata obtained during the test run, the process error values may bechecked at step 1776 to make sure that the values fall within apredetermined range, tolerance, etc. If the process error values do notpass this test, a further test run on a further test workpiece may beexecuted using a different predetermined electrical parameter set, as atstep 1778, and the method begins again. If the process error values meetthe test at step 1776, the control system 1765 derives a new electricalparameter set based on calculations including the set of process errorvalues and the values of the sensitivity table/matrix, as at step 1780.Once the new electrical parameter set is derived, the control system1765 directs power supply 1760 to use the derived electrical parametersin subsequent processing of further microelectronic workpieces toachieve the desired target physical characteristics, as at step 1782.

With reference again to FIG. 23, the exemplary system illustrates twopotential manners in which the first and second set of input parametersmay be provided to the control system 1765: a user interface 1784 and ametrics tool 1786. User interface 1784 may be comprised of, for example,a keyboard, a touch-sensitive screen, a voice recognition system, etc.Metrics tool 1786 may be an automated tool that is used to measure thephysical characteristics of the test workpiece after the test run. Whenboth a user interface 1784 and a metrics tool 1786 are employed, theuser interface 1784 may be used to input the target physicalcharacteristics that are to be achieved by the process while metricstool 1786 may be used to directly communicate the measured physicalcharacteristics of the test workpiece to the control system 1765. In theabsence of a metrics tool that can communicate with control system 1765,the measured physical characteristics of the test workpiece can beprovided to control system 1765 through user interface 1784. It will berecognized that other data communications devices may be used to providethe first and second set of input parameters to control system 1765, theforegoing being merely exemplary.

The foregoing method and apparatus can further be understood withreference to a specific embodiment in which the electrochemical processis electroplating, the thickness of the electroplated film is the targetphysical parameter, and the current provided to each of the individuallycontrolled electrodes 1758 is the electrical parameter that is to becontrolled to achieve the target film thickness. In accordance with thisspecific embodiment, a Jacobian sensitivity matrix is first derived fromexperimental or numerically simulated data. FIG. 25 is a graph of suchdata that can be used to derive the Jacobian sensitivity matrix data. Asillustrated, FIG. 25 is a graph of the change in electroplated filmthickness per change in current-time as a function of radial position onthe microelectronic workpiece 125 for each of the individuallycontrolled anodes A1-A4 of FIG. 23. A first baseline workpiece iselectroplated for a predetermined period of time using a predeterminedset of current values to individually controlled anodes A1-A4. Thethickness of the resulting electroplated film is then measured as afunction of the radial position on the workpiece. These data points arethen used as baseline measurements that are compared to the dataacquired as the current to each of the anodes A1-A4 is perturbated. Line1790 is a plot of the data points associated with a perturbation in thecurrent provided by power supply 1760 to anode A1 with the current tothe remaining anodes A2-A4 held at their constant predetermined values.Line 1792 is a plot of the data points associated with a perturbation inthe current provided by power supply 1760 to anode A2 with the currentto the remaining anodes A1 and A3-A4 held at their constantpredetermined values. Line 1794 is a plot of the data points associatedwith a perturbation in the current provided by power supply 1760 toanode A3 with the current to the remaining anodes A1-A2 and A4 held attheir constant predetermined values. Lastly, line 1796 is a plot of thedata points associated with a perturbation in the current provided bypower supply 1760 to anode A4 with the current to the remaining anodesA1-A3 held at their constant predetermined values.

The data for the Jacobian parameters shown in FIG. 3 may be computedusing the following equations: $\begin{matrix}{J_{mn} = {\frac{\partial t_{m}}{\partial{AM}_{n}} \cong \frac{{t_{m}( {{AM} + ɛ_{n}} )} - {t_{m}({AM})}}{ɛ_{n}}}} & {{Equation}\quad ({A1})} \\{{AM} = \begin{bmatrix}{AM}_{1} & {AM}_{2} & {\quad \cdots} & {AM}_{n}\end{bmatrix}} & {{Equation}\quad ({A3})} \\{t = {t({AM})}} & {{Equation}\quad ({A2})} \\{{ɛ_{1} = {{\begin{bmatrix}{\Delta \quad {AM}_{1}} \\0 \\\vdots \\\vdots \\0\end{bmatrix}\quad ɛ_{2}} = {{\begin{bmatrix}0 \\{\Delta \quad {AM}_{2}} \\0 \\\vdots \\0\end{bmatrix}\quad ɛ_{m}} = \begin{bmatrix}0 \\\vdots \\\vdots \\0 \\{\Delta \quad {AM}_{m}}\end{bmatrix}}}}\quad} & {{Equation}\quad ({A4})}\end{matrix}$

where:

t represents thickness [microns];

AM represents current [amp-minutes];

∈ represents perturbation [amp-minutes];

m is an integer corresponding to a radial position on the workpiece; and

n is an integer representing a particular anode.

The Jacobian sensitivity matrix, set forth below as Equation (A5), is anindex of the Jacobian values computed using Equations (A1)-(A4). Thesevalues are also presented as highlighted data points in the graph ofFIG. 25. These values correspond to the radial positions on the surfaceof a semiconductor wafer that are typically chosen for measurement.$\begin{matrix}{J = {\begin{matrix}0.192982456 & 0.071570577 & 0.030913978 & 0.017811705 \\0.148448043 & 0.084824387 & 0.039650538 & 0.022264631 \\0.066126856 & 0.087475149 & 0.076612903 & 0.047073791 \\0.037112011 & 0.057654076 & 0.090725806 & 0.092239186 \\0.029689609 & 0.045725646 & 0.073924731 & 0.138040712\end{matrix}}} & {{Equation}\quad ({A5})}\end{matrix}$

Once the values for the Jacobian sensitivity matrix have been derived,they may be stored in control system 1765 for further use.

Table 1 below sets forth exemplary data corresponding to a test run inwhich a 200 mm wafer is plated with copper in a multiple anode systemusing a nominally 2000 Å thick initial copper seed-layer. Identicalcurrents of 1.12 Amps (for 3 minutes) were provided to all four anodesA1-A4. The resulting thickness at five radial locations was thenmeasured and is recorded in the second column of Table 1. The 3 sigmauniformity of the wafer is 9.4% using a 49 point contour map. Targetthickness were then provided and are set forth in column 3 of Table 1.The thickness errors (processed errors) between the plated film and thetarget thickness were then calculated and are provided in the lastcolumn of Table 1.

TABLE 1 Data from wafer plated with 1.12 Amps to each anode. RadialMeasured Target Location Thickness Thickness Error (m) (microns)(microns) (microns) 0 1.1081 1.0291 −0.0790 0.032 1.0778 1.0291 −0.04870.063 1.0226 1.0291 0.0065 0.081 1.0169 1.0291 0.0122 0.098 0.099871.0291 0.0304

The Jacobian sensitivity matrix may then be used along with thethickness error values to provide a further, revised set of anodecurrent values that should yield better film uniformity. The equationssummarizing this approach are set forth below:

ΔAM=J⁻¹Δt (for a square system in which the number of measured radialpositions corresponds to the number of individually controlled anodes inthe system); and

ΔAM=(J^(T)J)⁻¹Δt (for a non-square system in which the number ofmeasured radial positions is different than the number of individuallycontrolled anodes in the system)

Table 2 shows the foregoing equations as applied to the given data setand the corresponding current changes that have been derived from theequations to meet the target thickness at each radial location (bestleast square fit). The wafer uniformity obtained with the currents inthe last column of Table 2 was 1.7% (compared to 9.4% for the test runwafer). This procedure can be repeated again to try to further improvethe uniformity. In this example, the differences between the seed layerswere ignored.

TABLE 2 Current adjustment Anode Currents Change Anode Currents forRun#1 to Anode Currents for Run#2 Anode# (Amps) (Amps) (Amps) 1 1.12−0.21 0.91 2 1.12 0.20 1.32 3 1.12 −0.09 1.03 4 1.12 0.10 1.22

Once the corrected values for the anode currents have been calculated,control system 1765 of FIG. 23 directs power supply 1760 to provide thecorrected current to the respective anode A1-A4 during subsequentprocesses to meet the target film thickness and uniformity.

In some instances, it may be desirable to iteratively apply theforegoing equations to arrive at a set of current change values (thevalues represented in column 3 of Table 2) that add up to zero. This maybe desirable when, for example, the processing recipe defined by theuser is entered using amp-minute values.

The Jacobian sensitivity matrix in the foregoing example quantifies thesystem response to anode current changes about a baseline condition.Ideally, a different matrix may be employed if the processing conditionsvary significantly from the baseline. The number of system parametersthat may influence the sensitivity values of the sensitivity matrix isquite large. Such system parameters include the seed layer thickness,the electrolyte conductivity, the metal being plated, the filmthickness, the plating rate, the contact ring geometry, the waferposition relative to the chamber, and the anode shape/currentdistribution. Anode shape/current distribution is included for the caseof consumable anodes where the anode shape changes over time. Changes toall of these items can change the current density across the wafer for agiven set of anode currents and, as a result, can change the response ofthe system to changes in the anode currents. It is expected, however,that small changes to many of these parameters will not require thecalculation of a new sensitivity matrix. Nevertheless, a plurality ofsensitivity tables/matrices may be derived for different processingconditions and stored in control system 1765. Which of the sensitivitytables/matrices is to be used by the control system 1765 can be enteredmanually by a user, or can be set automatically depending onmeasurements taken by certain sensors or the like (i.e., temperaturesensors, chemical analysis units, etc.) that indicate the existence ofone or more particular processing conditions.

The foregoing apparatus and methods may also be used to compensate fordifferences and non-uniformities of the initial seed layer of themicroelectronic workpiece. Generally stated, a blanket seed layer canaffect the uniformity of a plated film in two ways:

If the seed layer non-uniformity changes, this non-uniformity is addedto the final film. For example, if the seed layer is 100 Å thinner atthe outer edge than expected, the final film thickness will also be 100Å thinner at the outer edge.

If the average seed-layer thickness changes significantly, theresistance of the seed-layer will change resulting in a modified currentdensity distribution across the wafer and altered film uniformity. Forexample, if the seed layer decreases from 2000 Å to 1000 Å, the finalfilm will not only be thinner (because the initial film is thinner) butit will also be relatively thicker at the outer edge due to the higherresistivity of the 1000 Å seed-layer compared to the 2000 Å seed-layer(assuming an edge contact).

The foregoing apparatus and methods can be used to compensate for suchseed-layer deviations. In the first case above, the changes inseed-layer uniformity may be handled in the same manner that errorsbetween target thickness and measured thickness are handled. Apre-measurement of the wafer quantifies changes in the seed-layerthickness at the various radial measurement locations and these changes(errors) are figured into the current adjustment calculations. Usingthis approach, excellent uniformity results can be obtained on the newseed layer, even on the first attempt at electroplating.

In the second case noted above, an update of or selection all of the andother stored sensitivity/Jacobian matrix can be used to account for asignificantly different resistance of the seed-layer. A simple method toadjust for the new seed layer thickness is to plate a film onto the newseed layer using the same currents used in plating a film on theprevious seed layer. The thickness errors measured from this wafer canbe used with a sensitivity matrix appropriate for the new seed-layer toadjust the currents.

The Jacobian matrix analysis or other methods of determining how toselectively control the electrodes A1-A4 can also be used to carry outthe seed layer enhancement as set forth above herein, so as to create amore uniform seed layer across the face of the workpiece prior tosubsequent electrodeposition. Independent control of electrodes or banksof electrodes is particularly useful for tuning the reactor tocompensate for high resistance in the substream or barrier on which theseed layer is formed, both during seed layer enhancement and subsequentdeposition.

The foregoing apparatus and methods may also be used to compensate forreactor-to-reactor variations in a multiple reactor system, such as theLT-210C™ available from Semitool, Inc., of Kalispell, Mont. In such asystem, there is a possibility that the anode currents required to platea specified film might be different on one reactor when compared toanother. Some possible sources for such differences include variationsin the wafer position due to tolerances in the lift-rotate mechanism,variations in the current provided to each anode due to power supplymanufacturing tolerances, variations in the chamber geometry due tomanufacturing tolerances, variations in the plating solution, etc.

In a single anode system, the reactor-to-reactor variation is typicallyreduced either by reducing hardware manufacturing tolerances or bymaking slight hardware modifications to each reactor to compensate forreactor variations. In a multiple anode reactor constructed inaccordance with the teachings of the present invention,reactor-to-reactor variations can be reduced/eliminated by runningslightly different current sets in each reactor. As long as the reactorvariations do not fundamentally change the system response (i.e. thesensitivity matrix), the self-tuning scheme disclosed herein is expectedto find anode currents that meet film thickness targets.Reactor-to-reactor variations can be quantified by comparing differencesin the final anode currents for each chamber. These differences can besaved in one or more offset tables in the control system 65 so that thesame recipe may be utilized in each reactor. In addition, these offsettables may be used to increase the efficiency of entering new processingrecipes into the control system 65. Furthermore, these findings can beused to trouble-shoot reactor set up. For example, if the values in theoffset table are over a particular threshold, the deviation may indicatea hardware deficiency that needs to be corrected.

The anode arrangements described hereinabove, such as that illustratedand described in FIG. 9, are particularly well-suited for enhancing seedlayers that are deposited on highly resistive barrier layers orsubstrates, for plating microelectronic workpieces having highlyresistive seed layers as well as for plating highly resistive materialson microelectronic workpieces. Generally stated, the more resistive theseed layer or material that is to be deposited, the more the magnitudeof the current at the central anode (or central anodes) should beincreased to yield a uniform film.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A process for applying ametallization interconnect structure, comprising: (a) providing aworkpiece on which an ultra-thin metal seed layer has been formed usinga first deposition process, the first deposition process being avapor-phase deposition process that anchors the ultra-thin metal seedlayer to an underlying barrier layer, and the ultra-thin metal seedlayer being a non-continuous layer having voids; (b) repairing theultra-thin metal seed layer by electrochemically depositing additionalmetal on the ultra-thin metal seed layer within a principal fluidchamber of a reactor to provide an enhanced seed layer using a seconddeposition process, that is different from the first deposition process,comprising supplying electroplating power to a plurality of concentricanodes disposed at different positions within the principal fluid flowchamber relative to the workpiece; and (c) electrolytically depositing ametal on the enhanced seed layer under conditions in which thedeposition rate of the electrolytic deposition process is substantiallygreater than the deposition rate of the process used to repair the metalseed layer.
 2. The process of claim 1 wherein the additional metal iscopper.
 3. The process of claim 1 wherein the first electrochemicaldeposition step occurs in an alkaline bath.
 4. The process of claim 3wherein the alkaline bath comprises metal ions and an agent effective incomplexing the metal ions.
 5. The process of claim 1 wherein theultra-thin metal seed layer that is repaired is formed by physical vapordeposition.
 6. The process of claim 1 wherein the ultra-thin metal seedlayer that is repaired has a thickness of less than or equal to 500Angstroms.
 7. The process of claim 6 wherein the ultra-thin metal layerthat is repaired has a thickness of 100 to 250 Angstroms.
 8. The processof claim 1 wherein the complexing agent comprises one or more complexingagents selected from EDTA, ED, and polycarboxylic acid.
 9. The processof claim 8 wherein the complexing agent comprises EDTA and the EDTA inthe bath has a concentration within the range of 0.03 to 1.0 M.
 10. Theprocess of claim 8 wherein the complexing agent comprises ED and whereinthe ED in the electrolytic bath has a concentration within the range of0.03 to 1.0 M.
 11. The process of claim 9 wherein the complexing agentcomprises citric acid and the citric acid in the bath has aconcentration within the range of 0.03 to 1.0 M.
 12. The process ofclaim 1 wherein the step of subjecting the workpiece to a furtherelectrochemical deposition process occurs in an acidic electrolyticsolution to complete deposition of the metal to a thickness needed forthe formation of the interconnect structure.
 13. The process of claim12, further comprising subjecting the workpiece to a rinsing processafter electrochemical deposition in the alkaline bath and prior to thefurther electrochemical metal deposition process in an acidicelectrolytic solution.
 14. The process of claim 1, wherein the enhancedseed layer has a thickness at all points on sidewalls of substantiallyall recessed features distributed within the workpiece that is equal toor greater than 10% of the enhanced seed layer thickness over theexteriorly disposed surface of the workpiece.
 15. The process of claim1, wherein one or more of the plurality of concentric anodes used torepair the ultra-thin metal seed layer is disposed in close proximity tothe workpiece.
 16. The process of claim 15, wherein the plurality ofconcentric anodes used for the repair of the ultra-thin metal seed layerare arranged at varying distances may be from the workpiece from aninnermost one of the plurality of concentric anodes to an outermost oneof the plurality of concentric anodes.
 17. The process of claim 15,wherein the plurality of concentric anodes used for the repair of theultra-thin metal seed layer are arranged at increasing distances fromthe workpiece from an innermost one of the plurality of concentricanodes to an outermost one of the plurality of concentric anodes. 18.The process of claim 1, wherein one or more of the plurality ofconcentric anodes used to repair the ultra-thin metal seed layer is avirtual anode.
 19. The process of claim 18, wherein the virtual anodeused in the repair of the ultra-thin metal seed layer comprises an anodechamber housing having a processing fluid inlet and a processing fluidoutlet, the processing fluid outlet being disposed in close proximity tothe workpiece, and at least one conductive anode element disposed in theanode chamber housing.
 20. The process of claim 19, wherein the at leastone conductive anode element is formed from an inert material.
 21. Theprocess of claim 1, wherein the principal fluid chamber in which therepair of the ultra-thin metal seed layer is carried out is defined inan upper portion thereof by an angled wall, the angled wall supportingone or more of the plurality of the concentric anodes.
 22. The processof claim 1, wherein the repair of the ultra-thin metal seed layer iscarried out in a principal fluid flow chamber that comprises an inletdisposed at a lower portion thereof and that is configured to provide aventuri effect that facilitates recirculation of a chemical processingfluid in a lower portion of the principal fluid flow chamber.
 23. Theprocess of claim 1, wherein during the repair of the ultra-thin metalseed layer, at least two of the plurality of anodes are independentlyconnected to an electrical power supply, further comprisingindependently controlling the supply of electrical power to the at leasttwo of the plurality of anodes.
 24. The process of claim 23, wherein thecontrolling of the supply of power for at least one of the independentlycontrolled anodes is based on one or more user input parameters and aplurality of predetermined sensitivity values associated with theworkpiece, the predetermined sensitivity values corresponding to processperturbations resulting from perturbations of an electrical power supplyparameter for the at least one independently controlled electrode. 25.The process of claim 24, wherein the electrical power parameter iselectrical current.
 26. The process of claim 24, wherein the sensitivityvalues are logically arranged within a controller as one or moreJacobian matrices.
 27. The process of claim 24, wherein the at least oneuser input parameter comprises a thickness of the additional metal to bedeposited on the ultra-thin metal seed layer.
 28. A process for applyinga metallization interconnect structure, comprising: (a) providing aworkpiece on which an ultra-thin metal seed layer has been formed usinga first deposition process, the first deposition process being avapor-phase deposition process that anchors the ultra-thin metal seedlayer to an underlying layer, and the ultra-thin metal seed layer beinga non-continuous layer having voids; (b) repairing the ultra-thin metalseed layer by electrochemically depositing additional metal on theultra-thin metal seed layer within a principal fluid chamber of areactor to provide an enhanced seed layer using a second depositionprocess, that is different from the first deposition process, comprisingsupplying electroplating power to a plurality of electrodes within theprincipal fluid flow chamber, wherein at least two of the plurality ofelectrodes are interdependently connected to an electrical power supply,further comprising independently controlling the supply of electricalpower to the at least two electrodes during repair of the ultra-thinmetal seed layer; and (c) electrolytically depositing a metal on theenhanced seed layer under conditions in which the deposition rate of theelectrolytic deposition process is substantially greater than thedeposition rate of the process used to repair the metal seed layer. 29.The process of claim 28 wherein the additional metal is copper.
 30. Theprocess of claim 28 wherein the ultra-thin seed layer is formed on abarrier layer deposited on a surface of the workpiece.
 31. The processof claim 28 wherein the electrochemical deposition step occurs in analkaline bath.
 32. The process of claim 28 wherein the ultra-thin metalseed layer that is repaired has a thickness of less than or equal to 500Angstroms.
 33. The process of claim 28, wherein the controlling of thesupply of power for at least one of the independently controlledelectrodes is based on one or more user input parameters and a pluralityof predetermined sensitivity values associated with the workpiece, thepredetermined sensitivity values corresponding to process perturbationsresulting from perturbations of an electrical power supply parameter forthe at least one independently controlled electrode.
 34. At The processof claim 33, wherein the electrical power parameter is electricalcurrent or potential.
 35. The process of claim 33, wherein thesensitivity values are logically arranged within a controller as one ormore Jacobian matrices.
 36. The process of claim 33, wherein the atleast one user input parameter comprises a thickness of the additionalmetal to be deposited on the ultra-thin metal seed layer.
 37. A processfor applying a metallization interconnect structure to a workpiece onwhich an ultra-thin metal seed layer has been formed using a firstdeposition process, the first deposition process being a vapor-phasedeposition process that anchors the ultra-thin metal seed layer to anunderlying layer, and the ultra-thin metal seed layer being anon-continuous layer having voids, comprising (a) subjecting theworkpiece to an electrochemical deposition process that is differentfrom the first deposition process in an alkaline electroplating bathcomprising metal ions complexed with a complexing agent such thatadditional metal is deposited on the ultra-thin copper seed layer tothereby repair the seed layer resulting in an enhanced seed layer, thesecond deposition process being carried out by supplying electroplatingpower to a plurality of concentric anodes disposed at differentpositions relative to the workpiece within a principal fluid flowchamber of a reactor; and (b) electrolytically depositing a metal on theenhanced seed layer under conditions in which the deposition rate of theelectrolytic deposition process is substantially greater than thedeposition rate of the process used to repair the metal seed layer. 38.The process of claim 37 wherein the additional metal is copper.
 39. Theprocess of claim 37 wherein the ultra-thin seed layer is formed on abarrier layer deposited on a sur ace of the workpiece.
 40. The processof claim 37 wherein the complexing agent comprises one or morecomplexing agents selected from EDTA, ED, and polycarboxylic acid. 41.The process of claim 37 wherein the ultra-thin metal seed layer that isrepaired has a thickness of less than or equal to 500 Angstroms.
 42. Theprocess of claim 37, wherein during the repair of the ultra-thin metalseed layer, at least two of the plurality of anodes are independentlyconnected to an electrical power supply, further comprisingindependently controlling the supply of electrical power to the at leasttwo of the plurality of anodes.
 43. The process of claim 42, wherein thecontrolling of the supply of power for a given one of the independentlycontrolled electrodes is based on one or more user input parameters andthe plurality of predetermined sensitivity values associated with theworkpiece, the predetermined sensitivity values corresponding to processperturbations resulting from perturbations of an electrical power supplyparameter for the at least one independently controlled electrode. 44.The process of claim 43, wherein the sensitivity values are logicallyarranged within a controller as one or more Jacobian matrices.
 45. Theprocess of claim 43, wherein the at least one user input parametercomprises a thickness of the additional metal to be deposited on theultra-thin metal seed layer.
 46. A process for applying a metallizationinterconnect structure to a workpiece on which an ultra-thin copper seedlayer has been formed using a first deposition process, the firstdeposition process being a vapor-phase deposition process that anchorsthe ultra-thin copper seed layer to an underlying layer, and theultra-thin copper seed layer being a non-continuous layer having voids,comprising: (a) subjecting the workpiece to an electrochemicaldeposition process that is different from the first deposition processin an alkaline electroplating bath comprising metal ions complexed witha complexing agent such that additional metal is deposited on theultra-thin copper seed layer to thereby repair the seed layer resultingin an enhanced seed layer, comprising supplying electroplating power toa plurality of electrodes within the principal fluid flow chamber,wherein at least two of the plurality of electrodes are independentlyconnected to an electrical power supply, further comprisingindependently controlling the supply of electrical power to the at leasttwo electrodes during repair of the ultra-thin copper seed layer; and(b) electrolytically depositing a metal on the enhanced seed layer underconditions in which the deposition rate of the electrolytic depositionprocess is substantially greater than the deposition rate of the processused to repair the metal seed layer.
 47. The process of claim 46 whereinthe additional metal is copper.
 48. The process of claim 46 wherein theultra-thin seed layer is formed on a barrier layer deposited on asurface of the workpiece.
 49. The process of claim 46 wherein thecomplexing agent comprises one or more complexing agents selected fromEDTA, ED, and polycarboxylic acid.
 50. The process of claim 46 whereinthe ultra-thin metal seed layer that is repaired has a thickness of lessthan or equal to 500 Angstroms.
 51. An The process of claim 46, whereinthe controlling of the supply of power for at least one of theindependently controlled electrodes is based on one or more user inputparameters and a plurality of predetermined sensitivity valuesassociated with the workpiece, the predetermined sensitivity valuescorresponding to process perturbations resulting from perturbations ofan electrical power supply parameter for the at least one independentlycontrolled electrode.
 52. The process of claim 51, wherein theelectrical power parameter is electrical current.
 53. The process ofclaim 51, wherein the sensitivity values are logically arranged within acontroller as one or more Jacobian matrices.
 54. The process of claim51, wherein the at least one user input parameter comprises a thicknessof the additional metal to be deposited on the ultra-thin metal seedlayer.
 55. A process for applying a metallization interconnect structureto a workpiece on which an ultra-thin metal seed layer has been formedusing a first deposition process, the first deposition process being avapor-phase deposition process that anchors the ultra-thin metal seedlayer to an underlying layer, and the ultra-thin metal seed layer beinga non-continuous layer having voids, comprising: (a) repairing theultra-thin metal seed layer by electrochemically depositing additionalmetal on the ultra-thin metal seed layer within a principal fluid flowchamber of a reactor to provide an enhanced seed layer using a seconddeposition process that is different from the first deposition process;and (b) electrolytically depositing a metal on the enhanced seed layerunder conditions in which the deposition rate of the electrolyticdeposition process is substantially greater than the deposition rate ofthe process used to repair the metal seed layer, comprising supplyingelectroplating power to a plurality of concentric anodes disposed atdifferent positions within the principal fluid flow chamber relative tothe workpiece.
 56. The process of claim 55, wherein the seconddeposition process that repairs the seed layer is an electroless platingprocess.
 57. The process of claim 55, wherein the second depositionprocess that repairs the said layer also comprises supplyingelectroplating power to a plurality of concentric anodes disposed atdifferent positions within the principal fluid flow chamber relative tothe workpiece.
 58. A process for applying a metallization interconnectstructure to a workpiece on which an ultra-thin metal seed layer hasbeen formed using a first deposition process, the first depositionprocess being a vapor-phase deposition process that anchors theultra-thin metal seed layer to an underlying layer, and the ultra-thinmetal seed layer being a non-continuous layer having voids, comprising:(a) repairing the ultra-thin metal seed layer by electrochemicallydepositing additional metal on the ultra-thin metal seed layer toprovide an enhanced seed layer using a second deposition process that isdifferent from the first deposition process; and (b) electrolyticallydepositing a metal on the enhanced seed layer within a principal fluidchamber of a reactor under conditions in which the deposition rate ofthe electrolytic deposition process is substantially greater than thedeposition rate of the process used to repair the metal seed layer,comprising supplying electroplating power to a plurality of electrodeswithin the principal fluid flow chamber wherein at least two of theplurality of electrodes are independently connected to an electricalpower supply, further comprising independently controlling the supply ofelectrical power to the at least two electrodes during deposition. 59.The process of claim 58, wherein the second deposition process thatrepairs the seed layer is an electroless plating process.